Background
He was born Thomas L. Mahoney on July 9, 1924 in Fairibault City, Minnesota, the oldest of three children of John and Grace Mahoney. Tom's father was a casual laborer, doing odd jobs to support the family. Tom's early life and career are largely unknown to me, though it's to be expected he received his dance training in nearby Minneapolis-St. Paul.
In December 1955 Sidney Miller was hired as the new director for the Mickey Mouse Club. He seems to have been the one to bring Tom to Disney, and it's likely Tom worked with him earlier on The Donald O'Connor Show and The Colgate Comedy Hour.
Contribution
After viewing the first season, Walt Disney appears to have directed Sidney Miller, producer Bill Walsh, and the show's writers to pitch the second season at the twelve-year old level, instead of at the original range of three to fourteen. With the change in target audience came a major change in choreography. The first season choreographer, Burch Mann, came out of a ballet and folk dance background. Her style of choreography emphasized non-verbal story-telling, and included parts for dancers of all skill levels and ages.
For the second season, Tom's style of choreography would emphasize showmanship, displaying the virtuosity of the performer rather than trying to tell a story through dance. With an older cast, one that was uniformly strong on basic dancing skills, Tom could afford to devise more demanding steps, though the overall numbers were less complicated than the first season. He drew on a wide range of dance traditions, including popular dance, as well as tap, folk, jazz, and more rarely, ballet. His choreography usually paired-up boys and girls, generally no more than three couples, though there was little in the way of ballroom dancing. Instead, he followed the strengths and inclinations of the Disney Music Department, which favored music of the swing and early jazz era.
With the arrival of the third season, production numbers were cut drastically. The few new ones were of necessity simpler, due to a reduced budget, smaller cast and less rehearsal time. (To save money, replacement Mouseketeers were used as background extras in the serials, making them unavailable for some new dance numbers). Besides the Mickey Mouse Club, Tom also did the choreography for the Disneyland episode featuring the Mouseketeers, called the "Fourth Anniversary Show".
Tom himself was a very casual guy, who according to one Mouseketeer probably never owned a tie in his life. He wasn't universally appreciated by the Mouseketeers, at least one of them objecting to his emphasis on arm movement during dances. Tom appeared as a specialty dancer in The New Adventures of Spin and Marty, wearing a snowman costume. Besides doing the choreography for Annette, he also had a cameo as a haywagon driver. His most prominent on-camera performance came as a flamenco dancer, tapping away on a table-top, with Doreen as his non-dancing partner.
Aftermath
Tom continued to work as a choreographer for Disney Studio television productions up to the mid-sixties. His career highpoint came with the film Babes in Toyland (1962). Walt Disney wanted Annette Funicello to work with a choreographer she felt comfortable with in this first attempt at a Disney musical. Tom devised some simple routines for Annette that made her look good without taxing her talent. His large-scale Gypsy Dance spectacular was one of the few lively scenes in this otherwise limp movie.
About this same time, Tom Mahoney went with Walt Disney to see the Broadway production of My Fair Lady, starrring Julie Andrews. Tom later told friends that after the first few scenes, Walt said Julie would make a good "Mary Poppins", then promptly fell asleep for the rest of the performance. Tom missed out on doing the choreography for the film, his last Disney work coming with the Tenth Anniversary Show (1964) for the anthology series. Tom followed Annette to AIP, choreographing her and other dancers for Bikini Beach (1964). His last credited work known to me was for Paramount on Airplane! (1980). He died in St. Paul, Minnesota on May 28, 1995.