During a taping of The Tonight Show Starring Johnny Carson (1962), Jack Lemmon told this story. Prior to starting the film, the husband of co-star Virna Lisi made her promise that she would not be talked into doing a nude scene in her first American film. She assured him that she would not, signed the contract and traveled to Hollywood. While filming the "revelation" scene, where Lemmon awakens to discover in horror that he had gotten married at the bachelor party, she had to disrobe and lay in the bed nude but discreetly covered with a sheet. However, it was this day that her husband, an architect, arrived unannounced at the set to surprise his wife. When he walked into the scene, he became very upset. He focused his anger toward Lemmon who, realizing that discretion was the better part of valor, exited the set at full speed with Virna's husband in tow. Running past several sound stages on the MGM lot, he quickly found a garbage dumpster, jumped in and closed the cover. He waited there until security officers found him.
The comic strip art in the film was done by Mel Keefer, the artist on Perry Mason, Mac Divot and Rick O'Shay comic strips. In addition, Alex Toth drew a comic strip of the characters as part of a teaser campaign to promote the film.
There are at least two art pieces in Ford's apartment that are drawn/painted in the style of "Big Eyes" artist Margaret Keane, who was extremely popular at the time (it's not known whether these are authentic Keanes used for the movie or just lookalikes from the production department).
The trivia item below may give away important plot points.
When Harold is on the witness stand, he is asked what he would do with all of his money if he were single. His first reply is, "I'd have a little Chris-Craft maybe." In 1964, around the time this movie was in production, Chris-Craft introduced their very first fiberglass powerboat at the New York Marine Show. Up until then, they were known solely for wooden hulled boats, and came late to the fiberglass revolution. But when they did, they set the industry on fire. Fiberglass powerboats did not need the maintenance that wooden boats did, and they rode much more smoothly. Still, early models of fiberglass powerboats were quite expensive.