TV
Well do us all a favour and invent yourself some underpants!
— Passerby ‧ The Simpsons
Behind the line May contain spoilers.
Our reading
An editorial interpretation.
This is a heckle wrapped in sarcasm. The stranger tells someone to be useful and invent a basic piece of clothing, implying the person is lacking it. The joke is in treating an ordinary garment as a great invention that would help everyone nearby.
Context reviewed