Forgot Grandpa

Alright, listen up, buttercup. So, this dummy was at school and forgot their necklace. Big deal, right? But then they yell out, "Shit, I forgot Grandpa!" See, it's funny because they said "Grandpa" instead of "necklace". The joke plays on the listener's expectations to think that the speaker forgot an object, and the punchline is the speaker forgot their grandfather. You probably don't even know your grandfather. It is a very dark joke. You may need a therapist.