I Do, Adieu is the 26th and final episode of Season 5 of Cheers, and thus the season finale. It originally aired on NBC in the United States on May 7, 1987. It was Shelley Long's last regular appearance on Cheers before returning her film career, starting with Hello Again. This episode was written by show creators Glen Charles, and Les Charles, and directed by James Burrows.
Diane's ex-fiancée Sumner Sloan returns to Cheers to tell Diane that he gave one of her unfinished manuscripts to a colleague who was so impressed that he sent it to the publishers. Sumner warns her that finishing the novel will be impossible if she marries Sam. Sam envisions what life will be like when they're old and grey.
- Shelley Long as Diane Chambers
- Ted Danson as Sam Malone
- Rhea Perlman as Carla Tortelli
- John Ratzenberger as Cliff Clavin
- George Wendt as Norm Peterson
- Woody Harrelson as Woody Boyd
- Kelsey Grammer as Frasier Crane
Recurring / Guest stars:
- Michael McGuire as Prof. Sumner Sloan
- Walter Addison as Justice of the Peace
- Steve Giannelli as Steve
- This is Shelley Long's last regular appearance on the show. She reprised her role of Diane Chambers in the series finale One for the Road in 1993.
- This is the last appearance of the 1975 Paramount Television logo.
- Because this episode ran significantly longer than most, producers debuted a truncated version of the series intro that runs only 30 seconds (the original runs about 1 minute). For the remainder of the series, the shortened intro was used occasionally to accommodate unusually long episodes. Some syndication runs of "Cheers" use only the shortened intro, so as to allow the most commercials possible.
- To keep Shelley Long's departure from the series under wraps, three endings were shot: the aired ending, which had Diane leaving and promising to return in six months, one where Sam and Diane got married, and a third ending that the producers have not disclosed to this date.
- In a flash-forward sequence, grandfather Sam Malone asks Cliff Clavin when he is going to retire. Exactly one week before the 15-year anniversary of this episode, Cliff celebrated his retirement in an episode of Frasier. Also in attendance were Carla Tortelli and Norm Peterson.
- Philip Perlman (real life father of Rhea Perlman and "Cheers" writer-producer Heide Perlman) makes an uncredited appearance as a non-speaking wedding guest (he can be seen standing behind Carla as Diane walks down the aisle). Philip would later have a recurring role as the wise-cracking bar patron Phil, essentially taking over the one-liners from Al Rosen (Al), who passed away in 1990.
- This episode marks the final appearance of Michael McGuire as Prof. Sumner Sloan.