According to producer Jon Williams, Rilla Roo was created due to the game needing an eighth playable character, with the team coming up with the idea of a kangaroo. One of the first concepts for this role was a female character named "Kanga-Soo", but this was rejected by fellow producer Mark Cerny due to concerns about beating up a female character, and didn't make it past the modeling stage. According to artist Steve Bamford, the developers felt they needed "another Dingodile hybrid", spurring the creation of a different kangaroo named "Kangorilla", whose name was changed to "Rilla Roo" per the request of Sony due to trademark concerns.