1.John Krasinski had to cut his hair for Leatherheads, a movie he was doing, so he actually wore a wig during the last six episodes of Season 3.
2.Steve Carell has very active sweat glands, so the temperature on set had to be kept at 64°.
3.While filming Season 3, Episode 23, "Beach Games," Rainn Wilson accidentally kicked sand into Leslie David Baker's eye. He was rushed to the hospital because of a scratched cornea and he had to get his eye cleaned out.
4.The kiss between Michael and Oscar was actually improvised by Steve Carell, and the cast's reactions were completely genuine.
5.Bob Odenkirk was actually supposed to play Michael Scott because Steve Carell got cast in a show called Come to Papa. However, Come to Papa was canceled after four episodes so Steve was available again.
6.Rainn Wilson also auditioned for the role of Michael Scott.
7.Phyllis Smith was actually a casting associate for the show and read lines with many of the cast members during their auditions. The producers ended up liking her so much that they created a role for her.
8.B.J. Novak was actually the first person to be cast.
9.The cold open where Jim pops Dwight's fitness orb was a complete accident.
10.In the first season, they shot in an actual office building in Culver City, California. But for the rest of the series, they used a soundstage created to look exactly like the office.
11.John Krasinski shot the footage seen in the opening credits during a trip he took to Scranton, Pennsylvania after learning he was cast as Jim.
12.In Season 4, Episode 5, "Launch Party," Jim signs Meredith's cast "John Krasinski."
13.After they got cast, Steve Carell, John Krasinski, Jenna Fischer, and Rainn Wilson went to lunch and predicted that the show had the potential to last eight years.
14.Steve Carell is actually married to Nancy Ellen Carell, who played Carol Stills on the show.
15.The lactation consultant who helps Pam was actually played by Jenna Fischer's husband, Lee Kirk.
16.Mindy Kaling used to make up lies about her co-stars to trick B.J. Novak.
17.John Krasinski wrote a heartfelt note to Jenna Fischer about what their time on The Office meant to him, and that's the note he put inside Pam's teapot.
18.Rainn Wilson revealed that during Jim and Dwight's fight scenes, he and John would give each other tips — most of the best lines came from one another.
19.On filming days, John and Brian Baumgartner (who played Kevin) would spend lunchtime in John's trailer playing Madden Football.
20.The showrunners didn't tell NBC executives that Steve Carell would be returning for the series finale. During the table read, Creed read Michael's lines.
21.Bryan Cranston directed the "Work Bus" episode from Season 9.
22.Plenty of the cast members directed episodes too, like John Krasinski, Mindy Kaling, B.J. Novak, Paul Lieberstein, and Ed Helms.
23.In real life, Paul Lieberstein (who played Toby) is actually very shy and hated being on screen. Because of this, in the episodes Paul directed, Toby rarely had any lines.
24.The cast and crew wrote and shot way more footage than they ever needed — so much more that many of the episodes could've been twice as long.
25.During Season 4, Angela Kinsey was pregnant but her character wasn't. She can be seen hiding her stomach behind the handbags and filing cabinets for the majority of the season.
26.In the first season, the cast was told to bring in paperwork to keep busy because the computers on their desks didn't work.
27.But during the later seasons, the cast DID get working computers with internet.
28.While filming Season 5, production had to be shut down because John and Rainn couldn't stop laughing during Kelly's birthday party scene.
29.Finally, these two women who are in the pilot but never seen again were actually accountants from the production company.