[6] He was recruited to play soccer after starting on his high school team, but instead attended Amherst College with a major in American Studies.

[7] After seeing an improvisational comedy show at Second City iO Theater featuring Dave Koechner, Tim Meadows and Chris Farley, Besser began taking classes there.

Original members included Ian Roberts, Ali Farahnakian, Adam McKay, Rick Roman, and Horatio Sanz.

In 1993, UCB were regular guests on stage at the New Variety produced and hosted by R. O'Donnell at the Chicago Improv comedy club.

[8] While performing at the New Variety, Besser was cast and directed by O'Donnell in the New Year's Eve special Twisted, which aired on WFLD Fox 32 TV, Chicago.

[9] Twisted also featured Besser (and comedian Michelle Garb) in a series of improvised commercials directed by O'Donnell for McDonald's, Toyota, and Ameritech.

Besser went on to be the creator and co-star of the Redman & Method Man MTV hidden camera prank show Stung.

Besser has appeared in films such as Walk Hard: The Dewey Cox Story, Martin & Orloff, Year One, Undead or Alive, Drillbit Taylor, and Junebug, in addition to a number of sitcoms including Reno 911!, How I Met Your Mother, New Girl and alongside his wife Danielle Schneider in Community.

Besser and the UCB perform several times a week at the Los Angeles theater, in their show ASSSSCAT 3000 every Sunday night.

The show featured video shorts and sketches from Besser and Upright Citizens Brigade Theater comedians John Gemberling, Brett Gelman, Paul Rust, and Betsy Sodaro, and Nathan Barnett.

In 2014, Besser and comedian Rich Fulcher had an Adult Swim special air as part of the channel's "4AM Infomercial Parody" series, called In Search Of Miracle Man.