I can't say I came up with the idea, because I didn't. I actually saw these on a foodie blog (can't remember who) a few months ago and thought it would be a fun thing for me and my daughter to do.
I think they came out pretty dang cute. Almost as cute as my daughter. Actually...that's not true because my daughter is pretty freaking cute. She laughed so hard when we finished making the cupcakes and then proceeded to run around the house yelling "hamburger cupcakes" over and over.