Had things gone another way, Seth Rogen could have made his film debut opposite Eminem in “8 Mile” — had his audition not gone horribly wrong.

In his new memoir Yearbook, Rogen writes about trying out for the role of Cheddar Bob, dimwitted sidekick of Eminem’s B-Rabbit (the role ultimately went to Evan Jones), recalling the experience as “the weirdest audition I ever did.”

Because the movie’s casting director was uncomfortable with the actor’s “rappery” delivery of dialogue, auditioners were instructed to bring a friend to run their lines with.

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“Which is f**king nuts,” Rogen said in an interview with The Wrap.

As a result, Rogen invited pal Jason Segel (with whom he’d co-starred in “Freaks & Geeks”) to read with him, which is when he learned Segel was also auditioning for the same role.

“We asked our agents if our auditions could be scheduled one right after the other, so that one of us could audition for Cheddar, with the other reading the Rabbit part, and then we’d switch,” Rogen wrote. “We had a sleepover at my apartment the night before the auditions so we could rehearse and then carpooled to the audition together.”

However, having his pal as his scene partner became problematic when the dialogue they were reading made them crack each other up, such as “Yo, yo, mothaf**ka! It’s Chedda! What up, b***h!” and “Yo, yo, Rabbit! You gotta record your s**t at Paisley Park, yo!”

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“I started laughing hysterically,” Rogen admitted. “And so did Jason. We literally couldn’t make it through the auditions. As soon as one of us started the scene, the other would lose it… It was so silly, we couldn’t finish. We just excused ourselves and saw ourselves out, tears streaming down our faces.”

Looking back, Rogen can see it all worked out for the best.

“Auditioning is embarrassing in the best of times,” Rogen said, “Add the fact that one of my best friends is watching me do it and that we’re both reading for rappers from Detroit, which we could not have been less right for.”