I got the idea from this site, and I found it on Pinterest.
This is a fun way to create the mischievous (and curiously beloved) characters from Cat in the Hat, Thing One and Thing Two. I also chose it because it provided a fun way to encourage Jonah to touch paint- something which he has quite an aversion to!
First you paint the child's hand red, leaving out the ring finger and a small circular area in the palm. Help the child stamp their hand onto the paper. This is the Thing's body.Turn the paper around, so the print you just made is now on the bottom.
Clean the red paint off of the hand and paint the palm white and fingers blue. You can also paint the very top of the hand where the palm meets the fingers, blue. Help your child position their hand to stamp it just above the body.
Allow it to dry and then use a sharpie to draw the face. Paint a white circle into the open part of the red hand print. When that is dry, write either Thing 1 or Thing 2 in the circle.
It appears in some of the pictures, that the paper I used is white. It is actually a pale yellow. Manilla, light grey or beige would also work. Something that is a bit more than plain white, but not too bright or dark or it will not work well with the bright colors.