I'm interested in BDSM pet play (http://en.wikipedia.org/wiki/Animal_roleplay) and I was wandering, since I'm kind of curvy with big thighs, would I still be able to make a good BDSM pet or would I look stupid?

To an outsider, ANYONE engaging in pet play is going to look stupid, regardless f the size of their thighs or their body shape. So don't worry about what you look like and have fun. I know a couple of adult babies that have great relationships with their mommies, in spite of the fact that they are extremely unconvincing as babies (one of them is a hairy as a woolly mammoth, the other has a ZZ Top beard). Fun is the name of the game. After all, it's FANTASY, not REALITY.