Johnston starred on all three seasons of Comedy Central's The Sarah Silverman Program as "Officer Jay McPherson", the love interest of Sarah's sister Laura in the series. The series reunited Johnston with Mr. Show cast members Brian Posehn, Scott Aukerman, B. J. Porter, and Paul F. Tompkins. In 2011, Johnston appeared as a Sketch regular in season two of the Comedy Central Sketch comedy series Nick Swardson's Pretend Time.