It is a cup for low level Pokémon between level 15 to level 20. The sum of the levels of the three Pokémon chosen cannot be more than 50. Technically, all Pokémon except for Mewtwo and Mew are eligible to enter (although only Mew is listed as prohibited in the in-game rules list). However, obtaining Pokémon at such low levels, especially evolved Pokémon, can get quite complicated. While some are catchable at low levels in certain versions (e.g. level 15 Dragonair in Pokémon Yellow), others are more complex and involve trading with in-game Trainers, then trading these Pokémon to different in-game Trainers in different games.
Catch a low level VenonatY, then trade it for Tangela at the Cinnabar Island labRB. Trade Tangela for Parasect at Route 18Y. Breeding a Tangela in Generation II and trading it to Yellow is an alternative method.
Catch a low level SlowbroY, then trade it for Lickitung at the Route 17 gateRB. Trade Lickitung for Dugtrio at Route 11Y. Breeding a Lickitung in Generation II and trading it to Yellow is an alternative method.
In the Japanese Blue, trade a Kadabra for a Graveler at the Cinnabar Island lab. An eligible Golem cannot be obtained in the international Generation I games.
Catch a low level GrowlitheR, then trade it for Dewgong at the Cinnabar Island labY. Breeding a Growlithe in Generation II and trading it to Yellow is an alternative method.
Catch a low level Golduck, then trade it for Rhydon at the Cinnabar Island labY. Trade the Rhydon for a Kangaskhan at the Cinnabar Island lab in the Japanese Blue, then trade the Kangaskhan for a Muk in the Cinnabar Island labY. A low level Kangaskhan and Muk can only be obtained in international versions through trading with Generation II.
Catch a low level Golduck, then trade it for a Rhydon at the Cinnabar Island labY. In the Japanese Blue, trade the Rhydon for a Kangaskhan at the Cinnabar Island lab. International versions require trading a Kangaskhan over from Generation II.
Catch a low level KadabraGS and deposit it in a box in Pokémon Stadium 2. Withdraw it in Japanese Blue (to prevent it from evolving) and trade it for a Graveler at the Cinnabar Island lab.
Eligible but unavailable without cheats or glitches
The following Pokémon cannot be found at a low enough level in any game from Generation I or II to be used in the Pika Cup, and none of them are available as rentals.
Several of the Trainers use underleveled Pokémon. However, some of these Pokémon become eligible with tradebacks.
Mr. Fix uses a level 15 Magnemite in Round 1, which is unobtainable without glitches or tradebacks.
Hiker uses a level 15 Seadra in Round 1, which is unobtainable without glitches.
Swimmer uses a level 17 Seadra in Round 2, which is unobtainable without glitches.
Burglar uses a level 15 Tentacruel in Round 2, which is unobtainable without glitches.
Mr. Fix uses a level 15 Muk in Round 2, which is unobtainable without tradebacks or the Japanese Blue Version.
Fisher uses a level 15 Machamp, Kangaskhan, and Golem in Round 2. Level 15 Machamp and Kangaskhan are unobtainable without tradebacks, and a level 15 Golem is unobtainable without the Japanese Blue Version.
Some of the rental Pokémon are at an illegal level. All rentals are level 15, but not all species offered can be obtained at this level.
Ponyta, Seel, and Koffing are offered as rentals. They are only obtainable at level 15 with tradebacks, Without a Generation II game, their lowest possible levels are 28, 22, and 30, respectively.
Some of the rental Pokémon also feature illegal movesets.
Poliwrath knows Double Slap at level 15. This move is learned by its pre-evolved forms, Poliwag and Poliwhirl, at levels 25 and 26, respectively, while the maximum level allowed is level 20, meaning Poliwrath can not use Double Slap in the cup without glitches or tradebacks.
Cloyster knows Aurora Beam, Clamp, and Supersonic at level 15. These moves are learned by its pre-evolved form, Shellder, at level 30, 23, and 18 respectively. The maximum level allowed is level 20, meaning Cloyster can not use Aurora Beam or Clamp in the cup without glitches or tradebacks. It also cannot use Supersonic at level 15 without glitches or tradebacks.
Gyarados knows Hydro Pump, Leer, and Bite at level 15. While these moves are learned by Gyarados at level 1 in Red, Green, and Blue, it is not possible to catch a level 15 Gyarados in those games without glitches. A level 15 Gyarados caught in Yellow only comes with Tackle due to a change in learnset. Due to this, it is impossible for Gyarados to use Hydro Pump or Leer in the cup without glitches or tradebacks (with the latter requiring Pokémon Stadium 2's Move Relearner and the level 15 Gyarados on a Red, Green, or Blue cart). However, Bite can be used by a level 20 Gyarados, as it learns Bite at this level regardless of version.
Certain Pokémon are not offered as rentals, despite being available at a low enough level.
