Just recently when I was thinking about singing pets, I just remembered about the VW Polo dog. Where he sings loud when he and his owner are driving but sings quite when they are in the shops.
VW Polo Singing Dog
I felt this ad had the right amount of comedy and charm. When we see the dog singing, it comes off funny and weird. Yet we can still classify it as a dog because of it's characteristics. I believe this video will help inspire me if I was going for the singing pet route.