[1][2] He is credited with writing or co-writing numerous comedy films, including Old School, The Hangover: Part II, Semi-Pro, Road Trip, and many others.

[3][8][10] During this time, he met Todd Phillips whom he hired to direct a commercial for Miller Genuine Draft.

[6] Armstrong's production company, American Work Inc., has also produced several films and TV shows including Hesher, NBC's Best Friends Forever, a TV series adaptation of Problem Child, and the USA Network's Playing House (among others).

[16] The series—which Armstrong writes, directs, and produces—follows the exploits of a fictional version of Andrew Dice Clay and premiered on Showtime in 2016.

[7][8] Armstrong also co-hosts the UCB Sports & Leisure Podcast, alongside Matt Walsh.