"Poo poo head"

Austin and Avery have just started what I call the "poo poo head" stage. When they are playing together and want to be silly they start calling each other poo poo head and pootie and other silly names. Austin will sing songs in the car, but he will end the line with "pootie" Ex: The itsy bitsy spider went up the water pootie. Ugh, it drives me crazy. This has to be something they picked up at school and it's not a stage I am very fond of. The worst part is trying to be serious when telling them to stop. The other night Wes was getting on them at the dinner table and he said "We don't call our friends poo poo heads." I myself wanted to laugh at hearing Wes say poo poo head in such a serious manner. Oh the joys of parenthood!