Speed Bump

Alright, listen up, buttercup. The joke is funny because it compares a dead toddler to a "speed bump". Speed bumps are there to slow cars down. Calling a toddler a speed bump means the car ran over the toddler. It's funny because it's awful and the toddler is dead! You probably thought the toddler was sleeping! I bet you also think the Earth is flat! You dumb!