20 Things You Didn't Know About The 40-Year-Old Virgin

As terrific as the movie's ensemble cast is, it was almost even better, as Judd Apatow had originally written a part for his old pal Jason Segel - a character named Jason.

Sadly the director couldn't get approval from Universal to cast him, possibly due to Segel being little known at the time outside of his role on Apatow and Paul Feig's acclaimed series Freaks and Geeks.

Ultimately Apatow instead told Segel to use his own comedic voice to write a screenplay, leading to him penning 2008's Forgetting Sarah Marshall, which he also starred in to critical and commercial success.

Universal may have ended up kicking themselves over refusing Segel's casting, though, given that he became a major commodity the very next year by starring in hit sitcom How I Met Your Mother.