The following pictures don't give a full reflection of how hilarious this game is. It's something that Mason and Cooper came up with on their own. They often spend the morning this way and it cracks me up (when it's not making me want to rip out my hair). First Cooper will poke his head up above Mason's high chair tray. This makes Mason squeal with delight.
Then Cooper takes off and either runs around the dining room table or over to the front door in the other room. Mason goes absolutely wild with anticipation over this and starts squealing and waving his arms. He gets so excited I'm afraid he's going to bite through his top gum.
Then Cooper races back and "scares" Mason. To which Mason squeals.
PS -- Mason got the squeal/scream/screech that all the grandchildren (my nieces and nephew) on my husband's side of the family have. This is a high-pitched squeal that makes you want to chew tinfoil. But Mason more so than Cooper.