Here there are the Pokémon in the game that can be found in the Pokéballs. In this game there are the Pokéballs, which are normal, the Master Balls, in which there are only Legendary Pokémon and the Ultra Balls, in which there are Mega Evolutions. Here there are.
First Generation Pokémon
MegaBeedrill appears from an Ultra Ball and uses Pin Missile as a melee attack. It hits 16 times and inflicts 3% per hit.
Sandshdrew appears from a Pokéball and uses Sand-Attack to slow down close opponents.
Meowth appears from a Pokéball and uses Pay Day to throw coins to the opponents. It inflict a potential damage of 78%.
Alakazam appears from a Pokéball and uses Kinesis to move the opponents in the battlefield.
MegaAlakazam appears from an Ultra Ball and uses Psychic to move the opponents in the battlefield and inflict them 16% of damage.
Magnemite appears from a Pokéball and uses Magnet Rise to keep the caller unaffected by the low blast line and allows him to jump how many times he wants.
Farfetch'd appears from a Pokéball and uses Slash as a melee attack with normal damage (7%) but high knockback.
Electrode appears from a Pokéball and uses Self-Destruct. This move can damage even allies or the caller, inflicting them 28% of damage.
MegaKangaskhan appears from an Ultra Ball and uses Dizzy Punch. Both the mother and the daughter attack but the mother is stronger (18%, 9%).
Staryu appears from a Pokéball and uses Swift, following first an opponent, then attacking she or he. It inflict a total damage of 12%.
Magikarp appears from a Pokéball and uses Splash. It has no effect but you can use Magikarp as a bettering item. In this case, he won't disappear.
Ditto appears from a Pokéball and uses Transform to become another Pokémon.
Eevee appears from a Pokéball and evolves into a casual form.
Vaporeon is an Eeveelution. He uses Aqua Ring to restore the damage of his caller. The closer you stay to Vaporeon, the higher percentages he restores.
Jolteon is an Eeveelution. He uses Double Kick to attack two opponents. He performs two kicks on two different opponent. Both attacks inflict 8% of damage.
Flareon is an Eeveelution. He uses Heat Wave to inflict huge damages (40%+) to the opponents doing a similar move to Mario's old Final Smash Mario Finale.
Porygon appears from a Pokéball. It uses Sharpen to become a blade, a shield or a hammer. The blade inflicts the lowest damage (13%) but has the highest knockback, the shield stands in the middle (16%) and the hammer inflicts the highest damage (19%) but the lowest knockback.
MegaAerodactyl appears from an Ultra Ball and uses Roar to attack like Master Giant's waves.
Snorlax appears from a Pokéball and uses Body Slam to jump high and then land inflicting 38% of damage.
Moltres appears from a Master Ball and uses Fly to fly away, inflicting 40% of damage, a meteor smash and being an OHKO move.
Mew appears almost never from any Pokéball and tosses a CD. It's one of the rarest Pokémon along with Jirachi and Celebi, in fact their appearance's probability is 1/719.