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Parents: Raichu and Whimsicott
Shared egg group: Fairy
Offspring name: Raicott
New type: Electric/Grass
Base stats: 70/88/80/93/87/123 (BST: 541)
New ability and desc: (Static + Prankster) Lightning - This Pokémon's Electric-type attacks have their priority increased by one.
Notable moves: Volt...
I suggest that at least one of the three types, probably Light, should resist itself, because 9 of the 18 current Pokémon types resist themselves, and a Pokémon capable of producing bright lights is unlikely to take much damage if they are used on it.
Also Starmie could be Space/Light type...