Pedophile and Light Switch

Okay, listen up, you big dummy. So, a pedophile is a really bad person who likes kids in a way they shouldn't. A light switch turns something on. Get it? The joke is saying both "get turned on" by children. It's dark humor because it's about something terrible, pedophilia. It’s like, “haha,” but also, “eww,” all at once. You should probably not repeat this to anyone, ok?