Hawking's Anthem

Listen up, buttercup! The joke is all about Stephen Hawking, who was a super smart dude but couldn't stand up 'cause he was in a wheelchair, you uncultured swine. So, get it? The joke implies that he was being disrespectful because he remained seated during the national anthem. It's funny 'cause it's playing on his physical condition. You probably stand up to pee, so maybe that's why you didn't get it, ya goof!