He appeared many times on the game show "Hollywood Squares" in the late 1960s and 1970s. In one episode, Hackett (who was Jewish) 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.