Trivia Answer

It comes from an episode of The Simpsons,

"Grandpa vs Sexual Inadequacy"

Abe: [points to old TV] There she is, the old Radiation King! You'd park yourself right there and watch for hours on end.[young Homer's shadow is burned into the floor and wall]

[flashback to Homer watching Kennedy]

Kennedy: If I may, Helen, I'd like to respond to that question with yet another flip remark.[reporters laugh, sigh]

Homer: Wow. [walks into kitchen] Look at me, er, uh, Mom. I am,er, uh, President Kennedy.

Mrs. Simpson: Oh, Abe. Maybe our Homer could grow up to be President some day.

Abe: You, President? This is the greatest country in the world! We've got a whole system set up to prevent peoplelike you from ever becoming president. Quit your daydreaming, melonhead!

[back in the present]

Abe: Quit your daydreaming, melonhead!

It seems it is also featured in the video game Fallout 3.