When my oldest (who's only 6) was a little baby I did the usual "handprint" gifts for the fam. Do you know what I'm talking about? Oh, you know: handprint on a plate, handprint framed in a picture, handprint on a card, handprint on a t-shirt, etc. etc. But, it got really old after a while. So, I made some baby tushie prints. (Emphasis on BABY.)
This is a 2-person job. Slather the hiney in paint, press it firmly onto a piece of heavy paper or matte board & put it in a frame!