Proft broke into TV as a performer on "The Burns and Schreiber Comedy Hour" (ABC, 1973). He was a regular with Joey and Ray Heatherton on "Joey & Dad" (CBS, 1975), but soon after found steadier work as a writer for other performers. He was on the writing staff of "The Jim Stafford Show" (ABC, 1975), as well as ABC's revival of "The Smothers Brothers Show" (1975). Proft worked on specials for Cher, Bob Hope, and Ringo Starr, and also wrote for Cher's short-lived variety series (CBS, 1975-76). Even when Proft was performing again, it was usually secondary to his writing duties. He was a writer and performer on "Van Dyke and Company" (NBC, 1976) and both co-starred in and wrote for "Detective School", a short-lived ABC sitcom in 1979. TV work petered out in 1980, with Proft producing and writing two short-lived series, "Marie" (CBS) and "Buckshot" (ABC). He also appeared in a small role in the 1979 NBC TV-movie "Fast Friends".
Proft was determined to make the transition to feature films. His break came when, along with partner Neal Israel, he wrote the adaptation of "Bachelor Party" (1984), starring Tom Hanks. While that film was not a huge success, it was followed by "Police Academy" (also 1984), written with Israel and Hugh Wilson. Following the ribald adventures of recruits, "Police Academy" spawned six sequels and became one of the most successful film franchises in Warner Bros. history. By 1985, Proft Had added producer to his resume. He joined with Israel to write and executive produce "Moving Violations", a traffic school chronicle in the vein of "Police Academy", but not as successful. He and Israel had a modest hit with "Real Genius" (1985), featuring Val Kilmer as a college student with a high IQ. With Israel moving into directing, the duo parted ways that year. Enter the Zucker brothers (David and Jerry) and their cousin Jim Abrahams, who had scored with 1980's "Airplane!". Proft had first worked with them as part of their comedy troupe "Kentucky Fried Theatre" and later wrote an episode of their short-lived "Police Squad" (ABC, 1982). He reteamed with them to co-write the 1988 hit "Naked Gun", and later, with David Zucker, the sequel "Naked Gun 2 1/2: The Smell of Fear" (1991). Both were filled with puns and wordplay and featured a hilarious turn by Leslie Nielsen as Detective Frank Drebbin. With Abrahams, Proft began another hugely successful franchise, writing and producing "Hot Shots!" (1991) and the inevitable "Hot Shots! Part Deux" (1993), which utilized Charlie Sheen's little seen comic gifts. Proft moved on to the less successful, but equally juvenile "High School High" (1996).
Proft still occasionally appears before the cameras. He can be glimpsed as a maitre d' in "Modern Problems" (1981) and as a screaming man in "Bachelor Party" (1984).