In Pokémon Box: Ruby & Sapphire (where Bridgette is from), you would receive exclusive Pokémon eggs in-game for depositing a certain number of Pokémon, which themselves would hatch into Pokémon with moves not normally available in their learnsets.
A US version goes for a few thousand dollars used.
Oh, jeez... You came from just my feet.You're such a pervert, Yuuki-kun!Aa... I'm sorry. You're not angry, are you?I'll give you an egg, so please forgive me.