(I babysit a little girl who is very reluctantly undergoing potty-training. This means that she can sometimes spend a lot of time sitting on the potty while we wait. She’s also just learning about knock-knock jokes. Her mother is about to take over and let me go home.)
Daughter: “Knock knock, mommy!”
Mother: “Who’s there?”
Daughter: “Umm…tissue doggy!”
Mother: “Tissue doggy who?
Daughter: “Tissue doggy can you please let me off the potty now?!”