Your Mom and the Twin Towers

Okay, so basically, the joke is that your mom is super, duper fat. Like, so fat that when she stood on the Twin Towers, her weight made them collapse. It's a dark joke because it references a real-life tragedy, but the humor comes from exaggerating your mom's weight to an absurd degree. And you, yeah you, probably think that's hilarious because you probably think that adding 1+1 is rocket science. It isn't. And neither is your mom being able to fly. Get it?