Even before college, he had voiced a character on the Mister T cartoon show. LaMarr, unlike most of the other original nine cast members of Mad TV, had extensive television and film jobs experience when he joined the show. He has also improvised with Cold Tofu and Off the Wall. He studied improv at The Second City and at the ImprovOlympic in Chicago with Del Close. After graduating in 1989, he became a member of the award-winning sketch and improv comedy group The Groundlings. One of his biggest roles at Yale was the titular character in the British comedy Trevor. He is a graduate of the Harvard-Westlake School in North Hollywood and Yale University, where he helped found the improv comedy group Purple Crayon.