Lol, this is pretty funny. But the wierd thing is - I can't tell which chipmunk sings Nala or Simba. But Zazu sounds a lot like Simon, that's for sure. Here's what I know:
Simba=Theodore? Nala=Brittany? Zazu=Simon
I love the ending. It's super cute. ^.^ EDIT: Oh, wait... Why isn't the video showing?
I fixed the link for you CK and I think this is just a pitched changed version of the original IJCWTBK song. You speed anything up like that and it will sound like the chipmunks sang it, but nice find nonetheless and thanks for sharing. ^^
It's just a pitch change but being a huge Chipmunk fan I'd say, Alvin is Simba and Brittany is Nala. That makes more sense anyways, because Alvin and Britt like each other, and the same goes for Simba and Nala. You were right about Simon though.