The line comes from Batman & Robin, released in 1997, where Arnold Schwarzenegger played the villain Mr. Freeze. The character was written to deliver constant ice and cold related puns, and stay cool became one of the most quoted examples of that style. Clips and quotes from the performance circulated for years in forums, GIFs, and meme edits, keeping the joke alive long after the film. It remains popular because the earnest delivery makes even a groan worthy pun feel iconic and instantly reusable.