At the 1998 Oscar ceremony, when his name was announced as the winner of the Best Actor award, Jack Nicholson ascended to the podium by carefully stepping over the cracks between the tiles on the stage, in imitation of his character, Melvin Udall. Nicholson dedicated his Oscar to his A Few Good Men (1992) co-star J.T. Walsh who had died shortly before the Academy Awards in 1998.
In one scene the dog starts mimicking Jack Nicholson by stepping over the cracks in the sidewalk. The filmmakers accomplished this by placing little obstacles on the cracks so that the dog had to step over them. They then removed the obstacles digitally in post-production.
An earlier version of the script was called "Old Friends". It was listed as one of the best unproduced screenplays by Movieline magazine and had Kevin Kline and Mike Newell attached at one point to star in and direct it, respectively.
Jack Nicholson and Helen Hunt would win the Best Actor and Best Actress Oscars respectively for this film while Greg Kinnear was nominated for Best Supporting Actor. Nicholson is the only actor to date (c. 2015) to ever star in a film for which he would win the Oscar for Best Actor that would also receive a Best Actress Oscar and also be nominated for Best Supporting Actor. The previous one was One Flew Over the Cuckoo's Nest (1975) in which both Nicholson and Louise Fletcher won Oscars for Best Actor and Actress while Brad Dourif was nominated for Best Supporting Actor.
At the end of this film, when the credits begin to roll, the song "Always Look on the Bright Side of Life" performed for this film by Art Garfunkel, begins to play. Jack Nicholson and Art Garfunkel starred together in the film, Carnal Knowledge (1971).
The song "Always Look on the Bright Side of Life" was written by Monty Python's Eric Idle as the ending melody for the 1979 "Life of Brian." It has become a favorite in the UK for footballers and even funerals.
Shirley Knight's real-life actress daughter, Kaitlin Hopkins, has a cameo in this film. Her character bumps into Helen Hunt's character in the lobby. Helen Hunt plays the on-screen daughter of Shirley Knight.
When Melvin and Carol are in the restaurant in Maryland, the singer in the background is Danielle Brisbois, perhaps most recognizable for having played Archie and Edith's niece Stephanie on All in the Family. The song she is singing is Fallen, which was the love theme from Pretty Woman.