After even more research, TY 1 has a character named "Rufus", who is the generic red kangaroo enemy in the first level. In TY 2, that kangaroo is named "Roo", and he's unused. TY 2 has another unused kangaroo character named "Carniroo", who looks even more evil than Roo. The character code "RU" probably belonged to one of the two, but I didn't think it fit because they both look like enemies. Having lines as a friendly townie in Burramudgee Town didn't make sense. (That's what the CSZ2 lines are for.) Roo's texture in TY 2 is the same as TY 1, where he looks like a punk.

I took an educated guess with naming this one. Out of all the unused characters in TY 2 who didn't already have a voice, Gary seemed like the best fit. He was depicted as a koala scientist in a not-so-great mood in his concept art. I mean, this voice definitely would not have fit Andy the wombat or this other unused character named Rita, who's a giant female crocodile.