He has appeared in a number of television shows and movies, often portraying somewhat "ballistic" characters, especially on television shows. For example, on the Nickelodeon television series iCarly, he plays Lewbert, who is the mean and nasty doorman of Carly's apartment building. On Carly and Sam's webshow, they have a segment called "Messin' With Lewbert" where the two girls play pranks on Lewbert downstairs in the lobby of the building. On the show, Lewbert is recognized for having excessive anger outbursts, (i.e. when people walk all over the floor he just mopped).
Rowley has also appeared on The Amanda Show, most notably the sketch called "Blockblister" (a parody of the video retail chain Blockbuster), where he plays a customer who is angry because he did not get the movie he wanted (he paid for the video by tearing off his arm and giving it to them, replying "Keep the change!"). Again, he expresses his anger with loud outbursts in the scene.