After 17 years of playing Marvel’s most popular mutant, Hugh Jackman has revealed an embarrassing secret. When he was cast, Jackman had no idea what a wolverine was.

In fact, Jackman had no idea wolverines were even a real animal. For all that he knew he may as well have been playing a character named the Unicorn or the Hippogriff.

“I didn’t even know there was a wolverine. I literally, embarrassingly did about two weeks of research on wolves. I was rehearsing for three weeks and I was shooting, so I was kind of on my own. I remember going past an IMAX in Toronto, and there was an IMAX documentary about wolves, and so I thought, ‘I’ll go and see that’,” Jackman tells the Associated Press. It didn’t take X-Men director Bryan Singer long to realize that something was off about Jackman’s performance.

“He said, ‘Are you sort of walking funny, what’s going on?’ And I said, ‘I’ve been doing this thing with wolves,’ and he goes, ‘You know you’re not a wolf, right?’” Jackman remembered. Singer tried to clarify. “I said, ‘Well, there’s no such thing as a wolverine,’” Jackman said, to which the actor recalls Singer responding, ”‘Go to the zoo, dude.’ I literally didn’t know it existed.”

Jackman’s confusion over the difference between a wolf and wolverine would be revisited in X-Men Origins: Wolverine. That film includes a mythological story explaining why wolverines howl at the moon. Except that wolverines don’t howl at the moon. Wolves do. It is safe to say that Jackman grew into the role of Wolverine, concluding his run with Logan earlier this year, but this story does make you wonder if Russell Crowe knew that wolverines are real when he was being considered for the role. Logan has an 88.07 ComicBook.com Composite Score, which is the second-best ComicBook.com Composite Score among all comic book movies. Logan also has a 4.62 out of 5 ComicBook.com User Rating, making it the second most-loved comic book movie ever among ComicBook.com readers. Let us know what you thought of Logan by giving it your own rating below.

In Logan, in the near future, a weary Logan cares for an ailing Professor X in a hide out on the Mexican border. But Logan's attempts to hide from the world and his legacy are up-ended when a young mutant arrives, being pursued by dark forces. Logan is the final performance as Wolverine for Hugh Jackman. Jackman has played Wolverine for 17 years and through nine movies: the original X-Men trilogy, the prequel X-Men trilogy (though two of those appearances were cameos), and the Wolverine trilogy. Logan also introduces a possible heir to Wolverine's mantle in Laura, a.k.a. X-23, a clone young female clone of Wolverine with his claws, healing factor and fierce fighting skills.