The late John Mahoney was best known for portraying Martin Crane in Frasier, but he also played an entirely different character in Cheers. Airing from 1993-2004, Frasier was a hugely successful spinoff of Cheers, expanding the world of one of the sitcom's most popular characters. Although Frasier provided Mahoney with arguably his greatest role, there’s a poignant reason behind his earlier appearance in Cheers.
The Boston-set Cheers first introduced Kelsey Grammer’s Dr. Frasier Crane in season 3 and he quickly became a regular among the show’s barflies. Following Cheers’ conclusion, the recently divorced Frasier relocates to Seattle to host a radio show and reconnect with his family. Frasier sees the psychiatrist’s ex-cop father, Marty, move in with him, their conflicting personalities resulting in much of the show’s humor.
Mahoney excelled as Marty, his no-nonsense attitude the perfect antidote to Frasier and Niles' (David Hyde Pierce) elitism. However, Mahoney had already played a hack jingle writer in Cheers. Writing on his blog, Ken Levine, who worked on both Frasier and Cheers, revealed that Mahoney’s casting as Marty originated from another actor abandoning the Cheers role on show night. The producers’ last-minute replacement ultimately led to Mahoney landing his Emmy and Golden Globe-nominated role in Frasier, which ended after 11 seasons.
Mahoney guest-starred in Cheers season 11, episode 5, “Do Not Forsake Me O’ My Postman”. He played Sy Flembeck, whose jingles are all stolen from famous tunes, which is instantly called out by Kelsey Grammer's Frasier Crane. However, Levine, who co-wrote the episode, recalled the unfortunate story of the original actor disappearing from the Cheers set. Levine stated, “I will not reveal his name because he was a dear man, a good friend, no longer with us, and I don’t want him to be remembered for this.” The actor hadn’t worked in some time and was nervous the entire week leading up to show night, despite having performed live theatre and been in a popular 1970s sitcom. Levine believed he was “intimidated to be on Cheers” but his work didn't suffer. On the day the episode was to be taped, disaster struck. Levine continued, “The dress rehearsal went well. Everyone was happy. This actor then got in his car, drove off the lot, and never returned.” The writer was hugely sympathetic towards the actor, but his exit did lead to Frasier finding John Mahoney.
With a schedule to keep and the studio audience already in attendance, the episode had to be filmed, with Flembeck’s scenes postponed. John Mahoney was quickly cast, and the Frasier creators, who were in development on the spinoff, knew he would be great as Martin Crane. Thanks to his Cheers performance, Mahoney was used as a casting template when Frasier and its ensemble were pitched to NBC. In a guest post on Levine's blog, co-creator Peter Casey revealed that Mahoney was instantly granted pre-approval, alongside David Hyde Pierce and Jane Leeves as Daphne Moon. Frasier’s creators flew to Chicago to discuss the role with Mahoney. Despite being interested, he didn’t say yes until after reading the pilot script a couple of weeks later.
Mahoney’s casting boosted the writers’ enthusiasm for the spinoff, with the actor switching from a sleazy jingle writer to the endearing Marty. As Levine theorized in his blog, “the fate of Frasier and John Mahoney’s entire career” might have been very different, had the unnamed actor remained in Cheers. Coincidentally, Mahoney wasn’t the only Frasier actor to play a different character in Cheers – Peri Gilpin also guest-starred as a reporter in season 11, before replacing Friends icon Lisa Kudrow as Roz Doyle.