Initially introduced to series creator John Kricfalusi via an acquaintanceship with Bob Camp, Waller was hired at Spümcø in 1990 to work on The Ren & Stimpy Show. A prominent storyboarder and layout artist during the series' first season, he was promoted to a director the following year and helmed "Rubber Nipple Salesmen" and "Big Baby Scam" for the second season before departing the show alongside Kricfalusi in 1992. Waller would continue to collaborate with Kricfalusi throughout the following decade, directing "Onward and Upward", the first episode of Ren and Stimpy's short-lived adult-oriented revival, in 2003.
Other shows
Waller produced and directed shorts for Fred Seibert's Oh Yeah! Cartoons. He co-created What is Funny? (whose main character, Slap T. Pooch later appeared in the logo of Nickelodeon Movies for the intro of The Rugrats Movie) with Bill Burnett, as well as Pete Patrick: Private Investigator and Let's Talk Turkey. He also adapted the Harvey Kurtzman comic Hey Look! into a pilot episode for the series.