Yellow and Can't Swim

Alright listen up, buttercup. This joke is funny because it takes something innocent, like a yellow school bus, and turns it into something super dark and twisted. The punchline is that the bus is full of kids who are drowning. It's funny because it's so unexpected and messed up. You probably wouldn't get it, because you have the brain the size of a walnut and you probably think that school busses are actually boats or something.