It's always great when kids uncover books on their own. They tend to improvise to draw attention based on what they read, understand and feels funny from the book. I also have two good ones. (literally laughing as an adult before saying these)

What do you call cheese that isn’t yours? Nacho cheese

What did one wall say to the other wall? I’ll meet you at the corner

The bird & fly one is good. Stay young at heart. It helps.