One of the major pieces of The Office lore is, of course, the questions surrounding why in the world Jim’s hair looks so terrible in Season 3. John Krasinski’s shaggy hair became a staple of the fan-favorite Office character, but for one season there, something is a bit… off. It doesn’t look quite right. Well, that’s because in Season 3 of The Office, John Krasinski is wearing a wig.

Indeed, many Office fans did some digging and discovered that Krasinski was shooting a major role in the George Clooney-directed film Leatherheads during Season 3 of the show, and if you’ve seen Leatherheads you know that Krasinski does not have Jim’s trademark hair.

But the true story behind how Krasinski got approval to cut his hair and wear a wig for a season of The Office is a fascinating and kind of hilarious look behind the scenes of life on a hit broadcast TV show.

As recounted in Andy Greene’s book The Office: The Untold Story of the Greatest Sitcom of the 2000s, Krasinski was absolutely thrilled to land a starring role in Leatherheads. Just one problem: The Office creator and showrunner Greg Daniels did not want the actor to cut his hair. The show’s hairstylist Kim Ferry explained that Daniels was convinced fans would be able to tell Krasinski was wearing a wig:

“It would have meant cutting his hair into a 1920s hairstyle. But continuity-wise and contractually-wise, actors are obligated to keep their hair how it is for a series unless they get producer approval, of course. But it would have been cutting his hair super short, which would mean getting rid of the wings on the side and his long hair. He came to me and said, ‘Could we do a wig?’ He went to talk to them and said, ‘I really want to do this project.’ And they were like, ‘I think it would be obvious that it was a wig.’ Greg really felt like it won’t look like him.”

Krasinski would not be able to take the role in Leatherheads without getting a haircut, so he took a massive risk—he had Ferry make a wig in secret, and wore it while shooting a scene without telling anyone:

“Hiring a wig maker is not inexpensive. We did the fitting in his trailer and when it was done it looked amazing. It looked exactly like him. We were shooting him playing basketball at David Wallace’s house [“Cocktails”] and no one knows that I have this wig hidden in my side of the trailer now. He comes in. I put the wig on him, glue it down, take care of everything. And I go, ‘Okay, let’s do this, right?’ And he’s like, ‘Let’s do this.’”

Originally, Krasinski’s plan was to go to the producers and say, “See, I was wearing a wig and you couldn’t tell.” But the plan shifted—Krasinski actually wore the wig to go and talk to Daniels. Ferry recounted the story:

“John just vanished when the scene finished filming and I heard he drove back to the set. I jump in my car and I’m like, ‘Oh my God. Oh my God. What’s he gonna do?’ So I run over and I remember running up the stairs because the writers’ office was up on the top level. I walk down the hallway and my heart is pounding. I’m like, ‘Oh my God. What is happening?’ I walk in the room and Greg Daniels is sitting at his desk. I look at John and the wig is off. It’s sitting on Greg’s desk.”

As it turns out, Krasinski carried on a full conversation with his boss while wearing the wig, just to prove it could work:

“John told me later that Greg said to him, ‘John, I’ll know if it’s a wig. You can’t fake that kind of thing.’ As he’s staring at him with the wig on. And then John’s like, ‘Really? I don’t think you would,’ and he takes it off right in front of him.’ And then Greg said, ‘You win, I give you full permission to wear the wig.’ When I came in [Greg] said to me, ‘You guys have a lot of balls.’ For a minute I really thought I was going to get fired.”

So yeah, Krasinski and the show’s hairstylist took a pretty massive leap of faith to try and convince Daniels—and it’s a good thing it worked. Although the fact that fans have noticed Jim’s wig over the years is proof that it wasn’t an entirely seamless transition, and it’s kind of refreshing in the Season 3 finale when Jim gets a haircut for the corporate job interview and he finally gets to take the wig off.

For more on The Office, find out why Steve Carell left the show and how the writers originally planned to split up Jim and Pam in Season 9. All of these stories and more can be found in Greene’s book, which is available now.