Just having fun playing in the back yard and Liam decided the ball was soft. He is doing this lately where he feels something interesting so he lays his head down on it. If he likes it, the thumb goes in the mouth and he stays there for a few seconds. Then he is off and running again! He has put his head on me, the floor, the cats, the puppy, the grass, a cardboard box, Dan's shoes, the stairs, blankets, clean clothing piles, towels and a step stool so far. Only a few of them got the thumb.