Challenge Cup teams in Pokémon Stadium 2

It’s been a while, hasn’t it? I did have plans for having my next post be on Dragon Ball Z: Budokai Tenkaichi 2, but then I decided that to do that as well as I wanted I would first have to do one on Dragon Ball Z: Budokai 3 and I quickly lost interest during my playthrough of that.

But enough excuses! Today we’re going to dive into Pokémon Stadium 2’s Challenge Cup mode. For the sake of specificity, this was worked out on the NTSC-U version of the game.

Overview

Pokémon Stadium 2 is a game principally focused on battling. There are various cups, gyms, and a few other fights here and there. For most of them you get to use either your own Pokémon from the Game Boy and Game Boy Color games, or use rentals the game provides you with.

The Challenge Cup is special though, in that both you and your opponent have randomised teams. There are four divisions, called Poké Ball, Great Ball, Ultra Ball, and Master Ball. Each division has their own pool of types of Pokémon that can be used, with higher divisions generally offering stronger species. There is also a Round 2 mode to the game that unlocks after you finish all the battles, where you do everything again with harder opponents. In Round 2 the opponent’s Pokémon have higher stats, and the randomly generated Pokémon have access to a wider move pool.

These randomly generated teams are going to be the focus of this post, both the player’s and the AI’s. I will just be describing the main ideas without caring about the specific order the game actually makes all these decisions and calls the RNG. If you want that level of detail, I have written a replica of how the game does it which you can play with here. The repository is here.

Species selection

The four divisions each have their own pool of allowed species. These are:

Poké Ball	Great Ball	Ultra Ball	Master Ball
Bellsprout	Abra	Arbok	Aerodactyl
Bulbasaur	Aipom	Bellossom	Alakazam
Charmander	Ariados	Chansey	Ampharos
Chikorita	Azumarill	Charmeleon	Arcanine
Cleffa	Bayleef	Clefable	Blastoise
Cyndaquil	Beedrill	Dewgong	Blissey
Diglett	Butterfree	Dragonair	Charizard
Ditto	Chinchou	Dugtrio	Cloyster
Dratini	Clefairy	Fearow	Crobat
Drowzee	Corsola	Forretress	Dodrio
Ekans	Croconaw	Furret	Donphan
Exeggcute	Cubone	Girafarig	Electabuzz
Geodude	Delibird	Gligar	Electrode
Goldeen	Doduo	Golbat	Espeon
Grimer	Dunsparce	Granbull	Exeggutor
Hoothoot	Eevee	Haunter	Feraligatr
Hoppip	Elekid	Hitmonchan	Flareon
Horsea	Farfetch’d	Hitmonlee	Gengar
Igglybuff	Flaaffy	Hitmontop	Golduck
Jigglypuff	Gastly	Hypno	Golem
Krabby	Gloom	Jumpluff	Gyarados
Larvitar	Graveler	Kadabra	Heracross
Ledyba	Growlithe	Kingler	Houndoom
Machop	Houndour	Lanturn	Jolteon
Magnemite	Ivysaur	Magneton	Jynx
Mareep	Kabuto	Mantine	Kabutops
Marill	Koffing	Marowak	Kangaskhan
Nidoran♀	Ledian	Misdreavus	Kingdra
Nidoran♂	Lickitung	Mr. Mime	Lapras
Oddish	Machoke	Murkrow	Machamp
Paras	Magby	Noctowl	Magmar
Pichu	Magcargo	Octillery	Meganium
Pidgey	Mankey	Persian	Miltank
Pineco	Meowth	Pidgeot	Muk
Poliwag	Natu	Piloswine	Nidoking
Rattata	Nidorina	Ponyta	Nidoqueen
Remoraid	Nidorino	Pupitar	Ninetales
Sandshrew	Omanyte	Quagsire	Omastar
Seel	Onix	Quilava	Pinsir
Sentret	Parasect	Qwilfish	Politoed
Shellder	Phanpy	Raichu	Poliwrath
Slowpoke	Pidgeotto	Raticate	Porygon2
Slugma	Pikachu	Sandslash	Primeape
Smeargle	Poliwhirl	Seadra	Rapidash
Snubbull	Porygon	Seaking	Rhydon
Spearow	Psyduck	Shuckle	Scizor
Spinarak	Rhyhorn	Skarmory	Scyther
Squirtle	Skiploom	Slowbro	Snorlax
Sunkern	Smoochum	Slowking	Starmie
Swinub	Staryu	Sneasel	Steelix
Togepi	Teddiursa	Stantler	Tauros
Totodile	Tentacool	Sudowoodo	Tentacruel
Tyrogue	Togetic	Sunflora	Typhlosion
Venonat	Voltorb	Tangela	Umbreon
Vulpix	Wartortle	Venomoth	Ursaring
Wooper	Weepinbell	Vileplume	Vaporeon
Zubat	Wobbuffet	Weezing	Venusaur
	Yanma	Wigglytuff	Victreebel
			Xatu

To select the species, the game starts with a template. A template is a list of either Pokémon types or wildcards. For the player, the game randomly selects one of the following six templates:

• Electric / Ground / Water / * / * / *
• Electric / Fire / Water / * / * / *
• Rock / Grass / Water / * / * / *
• Electric / Ground / Flying / * / * / *
• Electric / Ground / Fire / * / * / *
• Rock / Fire / Grass / * / * / *

Each opponent also has two templates (since you face each opponent in two divisions), using the same templates in Round 1 and Round 2. These are:

Poké Ball
Camper Marcus	Fire	Fire	Ground	Ground	Ground	Ground
Rocket ♂	Poison	Poison	Poison	Poison	Poison	Poison
Picnicker Melissa	Flying	Flying	Flying	Flying	*	*
Guitarist Daren	Electric	Electric	Electric	Grass	Grass	Grass
Fisherman Curtis	Water	Water	Water	Water	Water	Water
Medium Peggy	Psychic	Psychic	Psychic	*	*	*
Rocket ♀	Normal	Normal	Normal	Normal	Normal	Normal
Juggle Dwight	*	*	*	*	*	*

Great Ball
Twins Jan & Jane	Bug	Bug	Bug	Bug	*	*
Schoolboy Oliver	Ground	Ground	Rock	Rock	Rock	Rock
Sailor Curt	Ice	Water	Water	Water	Water	*
Swimmer♀ Darcy	Normal	Normal	Normal	Normal	*	*
Officer Gerald	Fire	Fire	Fire	Grass	Grass	Grass
Kimono Girl Emiko	*	*	*	*	*	*
Scientist Roberto	Dark	Ghost	Psychic	Psychic	*	*
Gentleman Travis	*	*	*	*	*	*

Ultra Ball
Camper Marcus	Fire	Fire	Ground	Ground	Ground	*
Rocket ♂	Poison	Poison	Poison	Poison	*	*
Picnicker Melissa	Flying	Flying	Flying	Flying	Flying	*
Guitarist Daren	Electric	Electric	Grass	Grass	*	*
Fisherman Curtis	Water	Water	Water	Water	Water	Water
Medium Peggy	Ghost	Ghost	Psychic	Psychic	Psychic	*
Rocket ♀	Normal	Normal	Normal	Normal	Normal	Normal
Juggle Dwight	*	*	*	*	*	*

Master Ball
Twins Jan & Jane	Bug	Bug	Bug	Flying	Flying	*
Schoolboy Oliver	Steel	Ground	Ground	Ground	Rock	Rock
Sailor Curt	Ice	Ice	Water	Water	Water	*
Swimmer♀ Darcy	Fighting	Fighting	Normal	Normal	Normal	*
Officer Gerald	Fire	Fire	Fire	Grass	Grass	Grass
Kimono Girl Emiko	*	*	*	*	*	*
Scientist Roberto	Dark	Ghost	Psychic	Psychic	*	*
Gentleman Travis	*	*	*	*	*	*

The game generates a Pokémon for each element of the template. To do this, it creates a list of eligible Pokémon and then selects one at random. This is done in two steps.

Firstly the game looks at the template element. If it is a type, the game takes all the Pokémon eligible for the division with that type that are not already in the team. If it is a wildcard, the game takes all Pokémon eligible for the division that do not share a type with one already in the team. However, there is something of note with this: if a Pokémon is dual-typed and doesn’t share a type with anything already in the team, it gets added to the list twice.

The second step is done by the game to try and keep the base stat total average. The game looks at the average base stat total of the current team members and rounds it down (if this is the first Pokémon so the team is empty, the average is treated as 0). The game then divides the current list of candidates into two lists: one of Pokémon with a base stat total below the team average, and one with those that have a total at least as great as the average.

The game has target average base stat totals for each division, and these are 280, 360, 447, and 507. These turn out to be the average base stat total for all Pokémon eligible in each division, rounded to the nearest integer. The target is used to select which of the two lists to go with: if the target is below the team average, it will go with the below average list, else it will go with the at least average list. However, if the list chosen this way turns out to be empty, it will fall back on the other non-empty list instead.

From this it is clear some opponents will always have specific Pokémon because they ask for all of the eligible Pokémon with a given type. For example, in Ultra Ball Peggy’s template asks for two Ghosts. The only Ghosts in Ultra Ball are Haunter and Misdreavus, so she will always have these.

This type of thing can happen in a less obvious way as well though, like with Roberto in Great Ball. There is only one Dark and one Ghost in Great Ball, so he will always have Houndour and Gastly. Up to this point his average base stat total is thus 320. Now there are four eligible Psychics in Great Ball: Abra, Natu, Smoochum, and Wobbuffet. Only Natu and Wobbuffet have a base stat total of at least 320. If the game gives him Natu for the first Psychic, then his average will still be 320 so he will be forced to have Wobbuffet as his fourth team member. Thus, no matter what, Great Ball Roberto will always have Wobbuffet.

Moves

Ditto and Wobbuffet are special for move selection. Ditto always just has Transform, and Wobbuffet always has Counter, Destiny Bond, Mirror Coat, and Safeguard. For every other Pokémon, the following happens.

To decide the moves for each Pokémon, the game first creates a list of every move the Pokémon can learn up to its level (which is 30, 45, 60, and 75 for the four divisions) using the following procedure.

If the Pokémon is Smeargle, it starts by adding every move except Baton Pass, Metronome, Mimic, Mirror Move, Sketch, Sleep Talk, Struggle, and Transform. Next, it will add every move the Pokémon can learn from level-up in Gold and Silver up to its level. If the Pokémon is unevolved and can hatch from an egg, it will treat its level as 100 for this check. Then all moves that it can learn from a TM or HM in Gold and Silver are added.

If it is Round 2, the game will add additional moves to the learn pool. These are: egg moves, Crystal move tutor moves, Crystal level-up moves, RBY level-up moves, and RBY TM and HM moves. Note this does not include some legal moves like ExtremeSpeed on Dratini and Amnesia on Psyduck.

If the Pokémon is evolved, it will then repeat this procedure with its pre-evolution and add all the moves thus obtained. If the evolution is via level-up then the level will be decreased by 1 for this consideration, otherwise it is unchanged. However for this purpose, Tyrogue’s evolutions are not considered as being by level-up.

Next, the following moves are removed: Absorb, Bind, Bubble, Constrict, Dream Eater, Fire Spin, Fissure, Frustration, Guillotine, Hidden Power, Horn Drill, Leech Life, Lick, Milk Drink, Moonlight, Morning Sun, Nightmare, Poison Sting, Rage, Rapid Spin, Recover, Rest, Return, Rock Smash, Sketch, Sleep Talk, Smog, Snore, Softboiled, SonicBoom, Splash, Struggle, Synthesis, Teleport, Whirlpool, and Wrap.

Some opponents then have their own signature moves. These are:

• Fisherman Curtis: Rain Dance
• Guitarist Daren: Glare, Stun Spore, Thunder Wave
• Medium Peggy: Confuse Ray, Supersonic, Swagger, Sweet Kiss
• Officer Gerald: SolarBeam, Sunny Day
• Rocket ♀: Bite, Bone Club, Headbutt, Hyper Fang, Low Kick, Rock Slide, Rolling Kick
• Rocket ♂: Poison Gas (Poké Ball only), PoisonPowder (Poké Ball only), Toxic
• Schoolboy Oliver: Sandstorm
• Scientist Roberto: Double Team, Flash, Kinesis, Minimize, Sand-Attack, SmokeScreen, Sweet Scent
• Swimmer♀ Darcy: Attract

Any signature moves for the opponent that are in the move pool are removed and added to a special list. What remains is divided into four main classes of moves, whose members are given below.

Good support moves: Acid Armor, Agility, Amnesia, Attract, Barrier, Belly Drum, Charm, Confuse Ray, Cotton Spore, Destiny Bond, Double Team, Growth, Haze, Heal Bell, Light Screen, Lock-On, Mind Reader, Perish Song, Rain Dance, Reflect, Safeguard, Sand-Attack, Scary Face, Screech, SmokeScreen, Spikes, Spore, Substitute, Sunny Day, Swagger, Sweet Scent, Swords Dance, Thunder Wave, Toxic

Bad support moves: Baton Pass, Conversion, Conversion 2, Curse, Defense Curl, Detect, Disable, Encore, Endure, Flash, Focus Energy, Foresight, Glare, Growl, Harden, Hypnosis, Kinesis, Leech Seed, Leer, Lovely Kiss, Mean Look, Meditate, Mimic, Minimize, Mirror Move, Mist, Pain Split, Poison Gas, PoisonPowder, Protect, Psych Up, Roar, Sandstorm, Sharpen, Sing, Sleep Powder, Spider Web, Spite, String Shot, Stun Spore, Supersonic, Sweet Kiss, Tail Whip, Transform, Whirlwind, Withdraw

Good attacks: Aeroblast, AncientPower, Aurora Beam, Bite, Blizzard, Body Slam, Bonemerang, BubbleBeam, Crabhammer, Cross Chop, Crunch, Dig, Dizzy Punch, Double-Edge, DragonBreath, Drill Peck, Earthquake, Egg Bomb, Explosion, ExtremeSpeed, Faint Attack, Fire Blast, Fire Punch, Flame Wheel, Flamethrower, Fly, Giga Drain, Headbutt, Hi Jump Kick, Horn Attack, Hydro Pump, Hyper Beam, Hyper Fang, Ice Beam, Ice Punch, Icy Wind, Iron Tail, Jump Kick, Magnitude, Mega Kick, Mega Punch, Megahorn, Metal Claw, Octazooka, Outrage, Petal Dance, Psybeam, Psychic, Razor Leaf, Rock Slide, Rollout, Sacred Fire, Selfdestruct, Shadow Ball, Slash, Sludge, Sludge Bomb, SolarBeam, Spark, Steel Wing, Stomp, Strength, Submission, Super Fang, Surf, Swift, Take Down, Thrash, Thunder, ThunderPunch, Thunderbolt, Tri Attack, Twineedle, Vital Throw, Waterfall, Wing Attack

Bad attacks: Acid, AncientPower, Aurora Beam, Barrage, Beat Up, Bide, Bite, Bone Club, Bone Rush, Bonemerang, BubbleBeam, Clamp, Comet Punch, Confusion, Counter, Cut, Dig, Double Kick, DoubleSlap, DragonBreath, Dragon Rage, DynamicPunch, Egg Bomb, Ember, False Swipe, Faint Attack, Flail, Flame Wheel, Fury Attack, Fury Cutter, Fury Swipes, Future Sight, Gust, Horn Attack, Hyper Fang, Icy Wind, Jump Kick, Karate Chop, Low Kick, Mach Punch, Mega Drain, Mega Kick, Mega Punch, Metal Claw, Metronome, Mirror Coat, Mud-Slap, Night Shade, Octazooka, Pay Day, Peck, Pin Missile, Pound, Powder Snow, Present, Psybeam, Psywave, Pursuit, Quick Attack, Razor Leaf, Razor Wind, Reversal, Rock Throw, Rolling Kick, Rollout, Scratch, Seismic Toss, Selfdestruct, Skull Bash, Sky Attack, Slam, Sludge, SolarBeam, Spark, Spike Cannon, Steel Wing, Stomp, Submission, Swift, Tackle, Take Down, Thief, ThunderShock, Triple Kick, Twineedle, Twister, Vine Whip, ViceGrip, Water Gun, Wing Attack, Zap Cannon

There is some overlap between good attacks and bad attacks; anything in said overlap falls under both. Good and bad attacks are each further subdivided into four groups: STAB attacks of the Pokémon’s first type, STAB attacks of the second type (if the Pokémon is dual-typed), non-STAB physical attacks, and non-STAB special attacks.

With this set up, the moves can now be decided. For the first move, the game picks a random element of a specific class of move, the first of the following that has any moves at all:

• Good STAB attack (if dual-typed, one of the non-empty lists at random)
• Bad STAB attack (if dual-typed, one of the non-empty lists at random)
• Good non-STAB attack (one of the non-empty lists at random)
• Bad non-STAB attack (one of the non-empty lists at random)

After deciding the first move (and, in fact, after deciding the second and third moves too) the game will first remove all copies of that move from all the lists so it cannot be selected again. Then it will look at the added move and see if it is the first move of a combo. If so, it will add multiple copies of the second move of the combo to any lists said move is already in to make it more likely. The combos and the number of copies added are as follows:

First move	Second move	Copies
Giga Drain	Growth	3
Mega Drain	Growth	3
Zap Cannon	Lock-On	4
DynamicPunch	Mind Reader	4
SolarBeam	Sunny Day	3
Thunder	Rain Dance	3
Outrage	Safeguard	5
Thrash	Safeguard	5
Petal Dance	Safeguard	5
Rollout	Defense Curl	7
Reversal	Endure	7
Flail	Endure	7
Perish Song	Mean Look	7
Toxic	Mean Look	7
Swagger	Psych Up	7

There are two additional combos in the game that, due to a bug, are ignored: Toxic + Spider Web (7 copies) and Toxic + Pursuit (5 copies).

For the second move, the game first checks if the Pokémon is dual-typed. If it is, the game tries to add a bad STAB attack of the type other than that of the first added move. If there are no such options, it proceeds to the usual procedure.

The usual procedure is to first combine the lists of good physical and special non-STAB attacks and remove the ones that have the same type as the first chosen move. If this results in a non-empty list, a move is randomly selected from this list. However if this list is empty, the game picks at random either the list of good non-STAB physical attacks or good non-STAB special attacks. If one is empty, it just picks the non-empty one. Then a move is selected at random from the chosen list.

For the third move, the game first checks if any of the opponent’s signature moves are available. If so, it will pick one at random as the third move. If not, and there are any good support moves, it will first select one at random. If the selected good support move is already on the team, it will do another random pick of a good support move and go with that. This can be the one just rejected, so it is still possible for a good support move to appear multiple times on a team. If no good support moves are available, a random bad support move is chosen instead.

For the final move, the game looks at the Pokémon’s base stats. If the base attack is higher, the game will take all bad non-STAB physical attacks that are not of the same type as one of the first two moves chosen. If the base special attack is higher, bad non-STAB special attacks will be used instead. If they are tied, these lists are combined. The game then picks either this list or the list of available bad support moves at random (or goes with the non-empty one if one is empty) and picks a random move from it.

There is a subtle bug lurking here. The arrays containing the various types of moves are adjacent to one another, and are prefixed with their lengths. The arrays are large enough for the initial population of moves each Pokémon can learn, but they are not necessarily large enough to also fit in moves added due to combos. The game will then write past the end of the array, and in the process overwrite the next array’s length. This means the game could, for instance, pick Rain Dance as a bad support move due to the Thunder + Rain Dance combo, or pick a move past the array’s end. If the value in memory there is 0, no move is chosen so a three move Smeargle is possible.

Example from Werster, the Thunder + Rain Dance combo corrupted the next array

Held items

With the moves chosen, the next step is the held item. The game will do the below to decide a held item. If there is already a Pokémon on the team with that held item, it will try again and again until it gets one that isn’t.

There is a 116/256 chance the game will go for one of the following berry items, chosen at random: Berry Juice, Bitter Berry, Burnt Berry, Gold Berry, Ice Berry, Mint Berry, MiracleBerry, MysteryBerry, PRZCureBerry, or PSNCureBerry. If the selection is PSNCureBerry and the Pokémon is Poison or Steel, the game tries again as if a duplicate item were chosen. Similarly for Burnt Berry on Ice types and Ice Berry on Fire types.

There is an 89/256 chance the game will opt for the held item that boosts the power of attacks with the same type as the first move by 10%. If the type is Normal, one of the Pink Bow or Polkadot Bow is chosen at random. If the type is Dragon, one of the Dragon Fang or Dragon Scale is chosen at random. However if the first move is one of Counter, Dragon Rage, Mirror Coat, Night Shade, Pain Split, Psywave, Seismic Toss, or Super Fang, the game instead opts for the previous option of a random berry item.

There is a 38/256 chance the game will go for a random ‘hax item’, namely one of BrightPowder, King’s Rock, Quick Claw, or Scope Lens.

Lastly the remaining 13/256 chance is for a special species-exclusive item:

• Pikachu: Light Ball
• Farfetch’d: Stick
• Cubone/Marowak: Thick Club
• Chansey: Lucky Punch
• Ditto: Metal Powder

If the Pokémon is not one of these species, the game instead goes for a hax item as above.

After the held item is decided, the Pokémon’s moves are shuffled.

Stats and miscellany

DVs are generated randomly. Due to how Generation II works, this means Attack, Defense, Special, and Speed DVs are each random numbers from 0 to 15, and HP is determined by these. Shininess is determined by DVs, as is gender.

Shiny Pokémon have these sparkles, in case you think they’re common

Stat experience is set differently for the player and the AI. For the player, all of a Pokémon’s stats’ stat experience is set to the same value, namely (680 - Base Stat Total) * 65535 / 500 rounded down. For the AI, the same stat experience spread is used for all of their Pokémon, and this is higher in Round 2. Generally this is the same value for all stats, but a few trainers have speed stat experience set differently.

Trainer	Division	Round One Stat Experience	Round Two Stat Experience
Camper Marcus	Poké Ball	6400	9000
Rocket ♂	Poké Ball	12800	25600
Picnicker Melissa	Poké Ball	6000	36000
Guitarist Daren	Poké Ball	12800	28000
Fisherman Curtis	Poké Ball	20000	58000, but 30000 speed
Medium Peggy	Poké Ball	12800	32000
Rocket ♀	Poké Ball	20000, but 51200 speed	55000, but 65535 speed
Juggler Dwight	Poké Ball	36000	65535
Twins Jan & Jane	Great Ball	6400	8000
Schoolboy Oliver	Great Ball	11000	30000
Sailor Curt	Great Ball	25600	35000
Swimmer♀ Darcy	Great Ball	15000	27000
Officer Gerald	Great Ball	20000	40000
Kimono Girl Emiko	Great Ball	25600	50000
Scientist Roberto	Great Ball	22000	45000
Gentleman Travis	Great Ball	30000	60000
Camper Marcus	Ultra Ball	3200	4500
Rocket ♂	Ultra Ball	6400	22000
Picnicker Melissa	Ultra Ball	14000	35000
Guitarist Daren	Ultra Ball	12000	30000
Fisherman Curtis	Ultra Ball	16000	40000
Medium Peggy	Ultra Ball	7500	28000
Rocket ♀	Ultra Ball	14000, but 40000 speed	35000, but 65535 speed
Juggler Dwight	Ultra Ball	25600	50000
Twins Jan & Jane	Master Ball	500	3200
Schoolboy Oliver	Master Ball	7500	12800
Sailor Curt	Master Ball	12800	20000
Swimmer♀ Darcy	Master Ball	7500	18000
Officer Gerald	Master Ball	14000	30000
Kimono Girl Emiko	Master Ball	16000	35000
Scientist Roberto	Master Ball	12800	33000
Gentleman Travis	Master Ball	22400	47000

It might seem strange that higher division opponents tend to have lower stat experience, but bear in mind that the player will have less stat experience in higher divisions due to its dependence on the base stat total.

Friendship is a random value from 0 to 255 inclusive. While Return and Frustration are not possible to get in Challenge Cup, this can still come up due to Metronome.

Lastly Pikachu has a 1/256 chance of being a Talking Pikachu, which makes more anime-like sounds and is a result of using a Pikachu from Pokémon Yellow. Fun fact, a shiny Talking Pikachu is impossible in Challenge Cup due to some weaknesses in the random number generation. But that rant is for another post.

After all of this, the team members are shuffled and the team is complete.