Ironically, Mahoney actually appeared in the final season of Cheers before joining Frasier, but it was in a different role - a jingle writer named Sy Flembeck who actually shared a scene with Frasier Crane (Kelsey Grammer).
After starring in Frasier, Mahoney moved back to Chicago and acted with the Steppenwolf Theatre once again.
Mahoney passed away on Sunday in his long-time home in Chicago, Illinois, according to his publicist, Paul Martino.
John Cusack, who starred in the 1989 teen romantic comedy Say Anything with Mahoney, said that "anytime you saw him you left feeling better". His cause of death was from complications from cancer. With him came a Jack Russell terrier, Eddie, and a ghastly recliner chair he insisted on installing in his son's plush designer flat.
Mahoney's portrayal of Martin earned him two Emmy nominations, two Golden Globe nominations and a Screen Actors Guild award. Recently, he also had a recurring role on Hot in Cleveland, where he played a love interest of Betty White.
Mahoney was born in Blackpool, England in 1940.
Is Met Office expecting snow later this week in Kent?
The warning says: "There is a 90% probability of severe cold weather, icy conditions and snow between Sunday and Friday". However, widespread showers are expected to cross the country from the east from the afternoon through the evening.
In a 2015 interview, Mahoney recounted memories of huddling in an air raid shelter and playing among bombed-out houses.
"John was a beloved member of our Steppenwolf family who was known for his extraordinary kindness, generosity of spirit and quick smile", Steppenwolf spokeswoman Madeline Long said in a statement.
One sister, who moved to the Midwest after marrying a USA sailor, was responsible for Mahoney's decision to make his life in America.
The actor told the Associated Press in a 2015 interview that he fell in love with Chicago after visiting the IL city as a student.
"John's impact on this institution, on Chicago theater, and the world of arts and entertainment is great and will endure".
In 1979, having studied acting at St Nicholas theatre, Chicago, Mahoney turned professional on being invited by John Malkovich and Gary Sinise to join their fledgling Steppenwolf company in Chicago, which needed actors for older roles, and he continued to perform with it for the rest of his life.