In Supernatural‘s first season, Sam and Dean Winchester spent most of their time hunting down monsters you’ve heard of: Bloody Mary, Hook Man, etc. Flash forward 11 years, and the brothers are working in a world filled with angels, God, the Wizard of Oz, imaginary friends, and just about anything else you can think of. When it comes to story ideas on Supernatural, not even the sky’s the limit.

“[Show creator] Eric [Kripke] originally would say, you have to have Google-able monsters or Google-able urban legends,” executive producer Robert Singer tells EW of season 1. “We quickly realized we were going to run out of good urban legends in a hurry.”

In that moment, the show leaned a bit more into the mythology with John Winchester and the yellow-eyed demon, and from there, the show took off. From bigger monsters — what’s up, Lucifer? — to meta episodes — “Changing Channels,” “The Real Ghostbusters,” etc. — the show started taking more risks. “Eric used to say, ‘Smoke ’em if you’ve got ’em,’ which meant: Anything crazy, don’t be afraid to run it by us,” Singer says.

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All that being said, not every idea works. “I told Eric we shouldn’t do ‘Bugs,’ but we did, and he started listening to me a lot more after that one,” Singer says with a laugh, pointing to what’s considered the worst episode of the series.

But more recently than that, season 11 featured a story pitch that made it all the way to the script stage…but stopped there. “There was one last year that we actually tried to do and that was putting [Sam and Dean] in a game, Jumanji-style,” Singer says. “We just couldn’t make it work. I think that was the only script in 11 years that we ever abandoned. It was just too hard to do and we just couldn’t nail it.”

So I guess we’ll never get to see what Sam Winchester would look like as a monkey.