It’s a reference to an episode of The Simpsons, wherein Lisa’s boyfriend states: “I’m a level 5 vegan. I won’t eat anything that casts a shadow.”
Edit2: Primary source found.
It’s a reference to an episode of The Simpsons, wherein Lisa’s boyfriend states: “I’m a level 5 vegan. I won’t eat anything that casts a shadow.”
Edit2: Primary source found.