Hill was the original leader of the Impossible Missions Force, , in the series "" beginning in 1966. The phrase "Good morning, Mr. Briggs..." was a fixture early in each episode, where a sound or film recording he retrieved detailed the task he must accomplish. However, he was replaced in the show in 1967 after the end of the first season. As one of the few Orthodox Jewish actors working in Hollywood, he made it clear in advance of production that he was not able to work on the Sabbath (i.e., sundown Friday to dusk Saturday), and that he would leave the set every Friday before sundown. However, despite Hill's advance warnings, the show's producers were unprepared for his rigid adherence to the Sabbath, and on at least one occasion, Hill left the set while an episode was still in the midst of filming. The producers used a number of ways of reducing the role of Hill's character, Dan Briggs, whereby he would only obtain and hand out the mission details at the start of certain episodes, being unable to take further part in the mission as he was known to people they would encounter (used at least three times), or Briggs would need to don a disguise and another actor would then play his role "incognito" until the conclusion of the mission (and episode) when Briggs would peel off a face mask. On other occasions, Briggs was waiting to pick up the team at the end. Usually, Martin Landau's character (Rollin Hand) took over as the team leader for missions in Briggs' absence, Landau being initially a "special guest star" for the first season, not even included in the show's original opening credits.