Kirk made his feature debut that same year in the Disney Studio's first film about a boy and his dog, the classic "Old Yeller". He made a memorable impression as the 15-year-old boy who suddenly finds himself bearing the responsibilities of a man. Film historian Leonard Maltin, in his useful survey "The Disney Films", made the following sharp observation about Kirk's performance in this timeless tearjerker: "In many ways the outstanding performance of the film is that of Tommy Kirk, complete with Texas accent. His subsequent comedy roles in Disney films never gave him the scope of this characterization, and he carries off the full range of intense emotions with uncanny skill. Knowing that he was capable of this makes it all the more sad to watch him in the bumbling comedy parts he played later on."
Kirk did display a genuine flair for comedy, though, when playing the long-suffering son of such peevish Disney patriarchs as Fred MacMurray in "The Shaggy Dog" (1959) and Keenan Wynn in "The Absent-Minded Professor" (1961). He was also the gallant co-star of Annette Funicello in "Babes in Toyland" (1961), "The Misadventures of Merlin Jones" (1964) and "The Monkey's Uncle" (1965).
Kirk was banished from that redoubtable family entertainment empire for reasons that were mysterious at the time. He went on to play leads in American International Pictures' "beach party" movies and other low-budget teen fodder. Kirk and Funicello were paired in AIP's "Pajama Party" (1964) in which he portrayed a curious Martian teenager. His engaging Otherness was utilized again in the strangely sincere "Mars Needs Women" (1968). Kirk's other credits include "Swiss Family Robinson" (1960), "Bon Voyage" (1962), "Savage Sam" (the 1963 sequel to "Old Yeller"), "Son of Flubber" (the 1963 sequel to "The Absent-Minded Professor"), "Village of the Giants" (1965) and "It's A Bikini World" (1967). The middle-aged former juvenile lead finally revealed the surprising details of his departure in an unusually candid interview in MOVIELINE magazine (December 1992).