We learned that the set of the action flick (which opens May 23) was a fun place to be, but Jackman, 45, revealed that it wasn't always easy to get Fassbender (who plays villainous mutant Magneto) to join the party.
"Michael is one of those actors you had to coax out of the trailer. He'll wait in there for hours and hours – he's very difficult, very ornery on set," Jackman joked. "So there was really only one song [that would get him to come out], and I used to get the sound guy to play it very loud in the studio as he came in, just so he could get his mojo up."
That song was Robin Thicke's "Blurred Lines."
"I don't know what it was in that song or that video that got Michael going but there was something about it," Jackman said (the infamous video featured a bunch of naked models).
Norton then asked Fassbender, 37, to walk off stage and come back on as the hit played, and his costars played along.
Watch what happened next.