James McAvoy on Professor X look in 'Days of Future Past: 'I wanted to look like I smoke a lot of weed'

James McAvoy had a very specific vibe in mind when it came to how he'd portray Professor X in 2014's X-Men: Days of Future Past. Upon learning the superhero flick would be partially set in the 1970s, the Scottish actor thought it'd make sense for his version of Charles Xavier, also known by Professor X, to look as if he... well, smoked a lot of pot. 

The idea especially appealed to him so that the audience could see character development, since McAvoy and Patrick Stewart would come face-to-face as the younger and older versions of Professor X. 

"There was an opportunity to show a very different side of Professor X and Charles Xavier before he become the professor to make it interesting, to show he was a different person to begin with," McAvoy said in a new GQ video. "In preparation for X-Men: Days of Future Past, I thought, 'Well, I better shave my hair this time 'cause this is it now.'

"In prep for that, I got a buzz cut and just kind of just very close to sides and got a jarhead. I thought, 'I'll shave it further when I get there.' When I got to set, they were like, 'No, no, no, no, no.' I get the script and it's also set in the '70s and I was like, 'Right, we're doing hair extensions' and I'll get real seventies hair.'"

Stewart's Professor X is, of course, bald in the Marvel Comics-inspired film.

"When I found out that Patrick was going to be in the movie and look how Patrick does as playing Professor X, I wanted to go, 'I want to have long hair,'" McAvoy told GQ. "And I wanted to look like I smoke a lot of weed and maybe do a little bit of something stronger in the seventies and set in my purple haze just to show how far that journey is gonna have to be to make him into Patrick Stewart."

So, the actor asked the on-set person in charge of hair if it would be possible to get someone in to give him hair extensions.

"I had so little hair at this point," McAvoy adds. "So we found somebody and we did an 18-hour hair extension session in one sitting. ... And I just sat there for 18 hours going out of my mind. But, by the end of it, I looked like Professor X in Days of Future Past."

The hairy situation paid off, thankfully, with McAvoy getting his desired result. He also nailed the Cheech & Chong-friendly vibe, to boot.

Looking for more blockbuster cinema? Jurassic World Dominion, Nope, and Halloween Kills are now streaming on Peacock.