By entering these in the passwords menu, you'll get the designated Pokemon.

Effect	Password
Bulbasaur	74465213
Chandelure	94720173
Charizard	26495673
Dragonite	11009560
Eelektross	28563923
Garchomp	51830476
Gyarados	10599899
Gyarados (Shiny Forme)	94839985
Hydreigon	69283763
Oshawott	63664750
Piplup	19876976
Rotom	27453665
Serperior	10986334
Snivy (Shiny Forme)	20448123
Snorlax	71098343
Stunfisk	98993224
Zoroark	13540269