I made one with triplet baby bottoms and it was all molded rice krispy treats. The bottom was one piece, the legs and feet were separate and just placed together. The toes were balls of fondant. I covered the legs and feet in flesh covered fondant and the bottom in the colored diaper. I made the ruffles from a strip of fondant and placed it on the leg joint. I made little indentions in the feet and anything else to make it realistic. If you haven't covered RKT before, make sure you put a good layer of icing on it and smooth it out or you'll see the bumps through the fondant.
I hope this helps!
I found a tutorial for this: