“Boo.” “Boo who?”
“Don’t cry; it’s only a knock knock joke.”
A friend taught my informant this joke in elementary school. Like many knock knock jokes, it relies on using words with multiple meanings to give an unexpected punchline. And like some knock knock jokes, its annoying to the one hearing the joke, here because its suggested that they cry very easily (which could mean they are weak or oversensitive). My informant remembers disliking the joke for this reason, which is that it seems to trick the listener by taking their words to mean something they did not intend. My informant thinks it’s interesting because of this, though: because it shows that for some reason, there’s something people like about annoying others. They like pushing their buttons just to see what the reaction will be.
This is especially true in children I think, who want to see how people will react when they do something they suspect will annoy the person. Such a joke is also a form of teasing, which can make you feel above a person in a way. A child might want to feel that if they are insecure or just testing out social boundaries. Teasing, or jokes like this, can also be friendly, though, and used as a bonding event between people. Even though it’s at someone’s expense, it shows that the people involved are comfortable with each other and don’t mind making fun of one another.