I think we first did this thumb print craft in a preschool group, but we’ve done it a few times since then and it’s always a lot of fun.
The main idea is to make a thumb print, then with a marker or pen, add details to turn it into a critter. I bought a special stamp pad with washable ink to use for making thumb print critter art, but you don’t have to do that. Washable markers can be used too. Just cover the pad of the thumb with the ink and then press that spot onto the paper, and wash the ink off the thumb. Or you can keep some wet wipes at the table with you to avoid the kids having to get up and wash over and over again.
One thumb print makes a good spider or owl. Two together can give you a body and a head for a critter. A whole line of them could be a caterpillar. Just let the imagination go. It didn’t take long for my kids to start using whole hand prints in their thumb print art creations.
You don’t have to have great art skills to make cute pictures. They kids like that it feels kinda messy (but if you make sure to stick to washable inks, it isn’t really messy). It’s a fun way to spend some inside time when the kids need help for ideas of what to do.