Lamb 3 does this when he gets excited. He makes a fist with both hands, clenches his jaw, and shakes. He often does this instead of verbally answering "yes". While we were at communion yesterday, Lamb 3 started to do this when Ram got close to us. He got really excited while Ram gave him a blessing. I can only imagine how excited Lamb 3 will be when he gets to receive Christ's body and blood too.