Attention all ye Office fans: In an interview with Mashable, celeb hair stylist Kim M. Ferry just gave a whole bunch of insight into the work she did on The Office — including an entire saga involving John Krasinski's, aka Jim's, iconic shaggy bowl cut.
Basically, John had to cut his hair in order to appear in the movie Leatherheads and wanted to wear a wig to film the remaining episodes of The Office Season 3 — but the producers were basically like no way, we'll know if it's a wig.
As it turned out, both the producers and I sure can't tell the difference. John cut his hair anyway and went to another meeting with the producers, secretly wearing a wig he'd procured with the help of Kim.

In a moment that I sorely wish had been recorded, John was told once again that a wig would be too noticeable — only to whip off his wig and say that he'd already cut his hair.
As a result, this means that Jim's hair in the final six episodes is actually a wig. For reference, here's Jim in Season 3, Episode 2:

Ah, men's hair in 2006 — not unlike the overgrown pandemic 'dos of today:

Then here's Jim in Season 3, Episode 19, aka wig o'clock:

I don't know about you, but I sure can't tell the difference:

This means that Jim's iconic Dwight impersonation was also probably a wig:

However, in the Season 3 finale, Jim actually does get a haircut for his big interview with corporate — which we can now assume was his actual hair the whole time.

And, to quote Meredith's reaction:
