Him and Rick are twin bros in my AU bc there's this theory going around the Fandom that Rainbow and Rick are the same core, due to his voice, eye pattern and personality, but i wanted Rick to exist, and Rainbow too, not them ending as the same person, so be like 'wHy NoT mAkE tHeM tWiN bRoS'

His name when he was human was Riley

Rainbow is the symbol of LGBT to the lab, cuz of Rainbow's eye colour

Rainbow is 15 minutes older than Rick

He sometimes wears a red, orange, yellow, green, cyan, dark blue and purple slap bracelets on his arms, the bracelets are separate, not every colour on one bracelet, one colour is two bracelets

Rainbow is a Pokémon fan, along with Rick

And his favourite Pokémon is Eevee

Rainbow usually brings his backpack with him... i need to think of a reason why... gimme and moment... and he's the only core with a backpack

And he sometimes wears a sweater with the bisexual flag-