Showalter wrote and directed The Baxter (2005), in which he starred with Michelle Williams, Justin Theroux, and Elizabeth Banks.

Showalter is also a co-creator, co-producer, actor, and writer for the TV series Search Party.

[4] After he completed college, The New Group changed its name to The State and began creating video shorts for an MTV show called You Wrote It, You Watch It, hosted by Jon Stewart.

He played Ron Parker, the arrogant host of Cheap Seats, on ESPN Classic in the pilot episode.

However, after a bookcase fell on Showalter's character, tape librarians (and brothers) Randy and Jason Sklar took over the hosting duties.

He is also one half of The Doilies, an acoustic comedy band, in which he sings lead vocals opposite guitarist Zak Orth.

[9] Showalter also appeared in a series of commercials advertising the Toyota Yaris, starting in late 2011.

Showalter himself appeared as Gerald "Coop" Cooperberg and President Ronald Reagan in the series.

He also co-wrote and starred in the Netflix sequel Wet Hot American Summer: Ten Years Later which premiered in 2017.

[15] His 2017 film The Big Sick starred Kumail Nanjiani, Zoe Kazan, Holly Hunter and Ray Romano.

It saw a wide theatrical release and had an overwhelmingly positive 98% fresh rating on Rotten Tomatoes, and was nominated for the Academy Award for Best Original Screenplay.

Showalter next directed the 2020 film The Lovebirds, starring Kumail Nanjiani of The Big Sick, along with Issa Rae, Anna Camp and Paul Sparks.