Hawking's Cleaning Method

Alright listen up, you walnut! The joke is that Stephen Hawking was a famous scientist who used a wheelchair because he had a disease. Tesco is a British supermarket chain that also has car washes. The joke is funny because it implies that Stephen Hawking gets "washed" in a car wash because he's in a wheelchair and that's how he rolls. I know right, it's comedy GOLD. You probably still don't get it because your brain is smooth like a Ken doll.