Hackett was born in Brooklyn, New York to Anna (nee Geller) and Philip Hacker, an upholsterer and part-time inventor. He grew up on 54th and 14th Ave in Borough Park, Brooklyn, across from Public School 103 (now a yeshiva). He graduated from New Utrecht High School in 1942.
Stanley
Hackett starred as the title character on NBC-TV's Stanley, a 1956-57 situation comedy which ran for 19 weeks on Monday evenings at 8:30 pm EST. The half-hour series also featured a young Carol Burnett and the voice of Paul Lynde. The Max Liebman produced program aired live before a studio audience and was one of the last sitcoms from New York to do so. Stanley revolved around the adventures of the titular character (Hackett) as the operator of a newsstand in a posh New York City hotel. On September 30, 1960, he appeared as himself in an episode of NBC's short-lived crime drama Dan Raven, starring Skip Homeier, set on the Sunset Strip of West Hollywood.  After starring on Broadway in I Had a Ball, Hackett appeared opposite Robert Preston in the film adaptation of The Music Man (1962). In It's a Mad, Mad, Mad, Mad World (1963), Hackett was paired with Mickey Rooney, with whom he had also recently made Everything's Ducky (1961), in which they played two sailors who smuggle a talking duck aboard a Navy ship. Children became familiar with him as lovable hippie auto mechanic Tennessee Steinmetz in Disney's The Love Bug (1969).  He appeared many times on the game show Hollywood Squares in the late 1960s. In one episode, Hackett was asked which was the country with the highest ratio of doctors to populace; he answered Israel, or in his words, "The country with the most Jews." Despite the audience roaring with laughter (and Hackett's own belief that the actual answer was Sweden), the answer turned out to be correct. Hackett's regular guest shots on Jack Paar's Tonight Show in the early 1960s were rewarded with a coveted appearance on Paar's final Tonight program on March 29, 1962.

Q: Was Stanley a character he played?
A: Hackett starred as the title character on NBC-TV's Stanley, a 1956-57
What was the show about?
The half-hour series also featured a young Carol Burnett and the voice of Paul Lynde.
The half-hour series also featured a young Carol Burnett and the voice of Paul Lynde.