Patrick Stewart refreshing McAvoy on how to do the classic Patrick Stewart Scream.

James McAvoy plays young Professor Xavier in the new movie X-Men: Days of Future Past, and Michael Fassbender plays a young Magneto. Also in the film are Patrick Stewart and Ian McKellen, who play older, present-day Professor X and Magneto, respectively. So, you'd really hope they have impressions of them, otherwise everyone watching the movie would be wondering why McAvoy and Fassbender lost their Scottish and Irish accents and turned full-blown English.

Stewart and McKellan have been at this game a lot longer than their flashback counterparts, and between roles like Captain Picard and Gandalf, they've become figures that anyone who does impressions would like to take a crack at. James McAvoy has done P-Stew impressions in interviews before, so Sir Patrick ordered a command performance when they were both being interviewed by Yahoo! to promote X-Men. 

Of course, Patrick Stewart and Ian McKellen do everything together, so Ian McKellen demanded the same of Michael Fassbender. 

McAvoy's was the more authoritative impression, (although he was helped out by that clip of him doing it at a less intimidating moment), but Fassbender managed to work in some Shakespeare, so you gotta give him points for that.

Sources: Gawker