His notable credits include writing for Late Night with Conan O'Brien for seven years, and serving as co-creator, writer, and executive producer for Nathan for You, which aired for four seasons.

Between 2001 and 2008, Koman collaborated with fellow Late Night writers including Brian Stack and Andrew Weinberg, helping to create recurring characters and bits such as "The Interrupter" and "Hannigan the Traveling Salesman".

[3] When the show filmed a special episode in Finland following the discovery of O'Brien's rabid fan base there,[4][5] Koman and Weinberg, together with head writer Mike Sweeney, accompanied the host and helped generate the material.

[8] This segment also precipitated a rekindling of the ongoing romance between Koman and his future wife, Ellie Kemper, who had been both a writers' staff intern at the show and a regular performer in its sketches.

[9][10] Around the time of the release of the first-generation of Apple's iPhone in 2007, Late Night ran a fake advertisement purporting to show how multifunctional the new device was, with Koman and Kemper appearing together in this sketch.

Koman, reluctant to relocate with the rest of the Late Night staff from New York City to Los Angeles, accepted the role of head writer for Important Things with Demetri Martin.

Eagleheart, starring Chris Elliott as an outlandish US Marshal modeled in part on the titular hero of Walker, Texas Ranger, ran on Adult Swim for three seasons (2011–2014) and was backed by O'Brien's production company Conaco.

The multi-camera sitcom was inspired by a remote segment filmed at Chicago's The Wieners Circle for the TBS instantiation of O'Brien's late night talk show (called simply Conan).