Leichliter's career in animation began in 1975 when he worked on You're a Good Sport, Charlie Brown. This was followed by numerous other Peanuts specials that he was a crew member of throughout the late 1970s and 1980s. Since then, he has worked on many animated television series, particularly those made for Nickelodeon, which include Hey Arnold!, ChalkZone, The Fairly OddParents, CatDog, SpongeBob SquarePants, The Mighty B!, and Catscratch. Leichliter more recently was a director for the Cartoon Network original series Adventure Time, for which he directed 114 episodes and the original short. Adventure Time also garnered him three Primetime Emmy Award nominations in the category "Outstanding Short-Format Animated Program" in 2010, 2011, and 2012.