Potato Printing is a classic I remember doing this with my mum. I was chopping up spuds for shepard's pie and i had a lot so I thought why not do some fast spud faces. I used a ball point pen and just kinda jabbed at it then I used the scoopy pointy end of the potato peeler to clear out the pulpy excess. I also cut little handles into the back of the spud so they would be super easy for little tiny boys to use. Results could have been a bit better, activity only lasted 10 mins, but the stamps will keep if you wash them and pop them into a plastic bag and put them in the fridge. The paper makes great wrapping, and an older child could draw bodies for the spuds at a later date. The stamps turn out best if you really slam them into the paper so next time I'm going to encourage some rough stamping and see if I can stretch it out to 20 mins, maybe i need some glitter paint? printing ink would give you the best results for this, but we just used some acrylic paint that we already had. Go see if you have any tato's floating around just asking for a stamping.