One HP

Alright, listen up, dummy! Stephen Hawking, may he rest in peace, was, like, super famous for being a genius scientist, right? But he was also, you know, had a disease that made it hard for him to move. So, the joke is saying he's got only one hit point, like in the game Fortnite, because he's not exactly in tip-top physical shape. You probably play Fortnite all day and are in bad shape too, so you have something in common with Stephen Hawking!