HAHAHA Sadie does that with roll over. Once she figured that one out, she'll roll over any time she wants a treat. I'll have a treat in my hand and I might pause (usually because I'm trying to decide which trick I'd like her to do...I don't ask for the same one all the time) and if I take to long, she'll just roll over. Like
"OK I did something & you KNOW it was cute, can I have it now?"