Have you ever walked in to Stephen Hawking's house?
No, neither has he.
Hawking's House
Explanation
Explain Bear
Listen up, buttercup. This joke is about Stephen Hawking, who used a wheelchair because he had a disease called amyotrophic lateral sclerosis (ALS). The joke plays on the fact that because of his condition, he couldn't walk into his own house. Bet you feel silly now!