Harmon portrayed a highly fictionalized version of Ted Templeman on two episodes of the Channel 101 web series Yacht Rock, a satirical history of soft rock, featuring stories about Templeman's collaborations with The Doobie Brothers, Michael McDonald and Van Halen.

He was the creator, executive producer, and a featured performer in Acceptable.TV, a Channel 101-based sketch show airing for eight episodes in March 2007 on VH1.

[10] On May 23, 2011, Harmon began hosting a monthly live comedy show and podcast at Meltdown Comics in Hollywood called Harmontown.

The documentary, also called Harmontown, was produced by director Neil Berkeley that follows Harmon, Davis, McGathy, and Crittenden.

[11][12] On September 10, 2019, the Harmontown Twitter account announced that the podcast would be coming to an end,[13] and its final episode was published on December 5, 2019.

It has also produced season 2 of Mary Shelley's Frankenhole and the special Beforel Orel for Adult Swim, HarmonQuest for Seeso and VRV and Animals for HBO.

[17] The studio's output declined steadily after the departure, with their only released projects after 2020 being The Freak Brothers and Slippin' Jimmy.

In January 2023, Harmon became the sole showrunner after Roiland was dismissed from the series amidst domestic assault charges.

Club in July 2017 that Harmon and Evan Katz would adapt Kurt Vonnegut's 1959 novel The Sirens of Titan into a television series.

[26] Harmon adapted the hero's journey, a well-known storytelling framework, for use in television; he calls this technique the "story circle".

[27] He began developing the technique while stuck on a screenplay in the late 1990s, and wanted to codify the storytelling process to unveil the "structure" that powers movies and TV shows.

[28] This prompted him to simplify Joseph Campbell's structure of the hero's journey into a circular eight-step process that would reliably produce coherent stories.

He writes the steps as follows: Campbell's structure of the hero's journey is the main influence in Harmon's technique.

Asthma inhalers, eyeglasses, credit cards, fratty boyfriends, promotions, toupees, and cell phones can't save you here.

[33] In an interview with Collider, writer Adam Chitwood said, "Rick and Morty debuted in 2013 to a serious degree of anticipation, as it marked a new animated venture for Community creator Dan Harmon, but it was the marriage of Harmon's adeptness for structure and character and co-creator Justin Roiland's insanely creative/sometimes insane mind that made Rick and Morty much more than just another animated TV series for adults."

In an interview with Vulture, Harmon named a number of films, television shows, books, and artists that have shaped his writing style.

This includes the films RoboCop and Network; the television shows Cheers, Mr. Show, Arrested Development, Second City Television, and Twin Peaks; the books Slaughterhouse-Five and The Hitchhiker's Guide to the Galaxy; the play Sexual Perversity in Chicago; and writers, artists, and comedians including Garry Shandling, George Lucas, Spalding Gray, Charlie Kaufman, Woody Allen, Tom Kenny, and Chris Elliott.

[34] In the same Vulture interview, Harmon mentioned Dungeons & Dragons, musician Tori Amos, and evolutionary anthropologist Elaine Morgan as influences.

[34] He singled out Morgan's aquatic ape hypothesis, calling it a "peaceful, interesting, mythical concept, and a scientific one, that maybe the origin of Homo sapiens was kind of a fairy tale".

[34] For Rick and Morty, Harmon and co-creator Justin Roiland listed a number of influences on the show's style, including, Saturday Night Live, The Hitchhiker's Guide to the Galaxy, Doctor Who, and the cult sci-fi film Zardoz.

[38][27] On a podcast hosted by Kevin Pollak, he said, "I know I'm not normal, but I think the important thing is that [...] I started to discover that I had a lot more in common with Abed than I did with Jeff.

[46] After the exchange, he made a lengthy apology on his podcast Harmontown and went into detail about his wrongdoings, which included making advances on Ganz and then mistreating her after she turned him down.