Although James Stewart is 6'4'', he refers to Harvey as being 6'3 1/2'' tall in the film and looks up at him during the entire film. That's because this is Harvey's height in the original play by Mary Chase. In a 1990 interview, Stewart said that he had decided that for the film, Harvey was going to be 6'8'', so that he could indeed look up at him.
Though James Stewart's character, Elwood P. Dowd, may certainly be referred to as an alcoholic, only at one time in the entire picture is he seen taking a drink. This is because the Hollywood Production Code at the time would not allow him to be shown getting drunk on film.
Prior to the release of the film, a press release reported that Francis the Talking Mule would make a cameo appearance. James Stewart, as Elwood P. Dowd, was to walk past Francis, and Francis was to "speak". Elwood would turn, in order to respond, but Francis would rebuke him, stating that he was talking to the big rabbit.
Henry Koster and James Stewart discovered that they worked extremely well together. Koster said later that working with Stewart was "without any doubt one of the most pleasant experiences of my life...It must have been his spirit. There was very little friction, ever, only ambition and craftsmanship and precision, just doing it right professionally. On top of that he put the whipped cream of great talent...He was always the first on the set."
Mary Chase had the idea that film audiences should actually see Harvey at the end of the film because she "didn't want anybody to go out of the theater thinking Elwood is just a lush. He believes in Harvey...and I think the audience ought to believe in Harvey, too." The studio reportedly considered this and experimented with how to show him to the audience, including his appearance in silhouette, and even by attaching a rabbit tail to the taxi driver at the film's conclusion. In the end, however, the studio won out and wisely decided NOT to ruin the illusion. Only once had a giant rabbit actually appeared on stage in the play of Harvey, and the results were disastrous. Theatrical Producer Brock Pemberton recalled in a 1945 interview that at that performance in Boston, "a chill descended on the gathering, which never quite thawed out afterwards."
Twenty years after the film's release, James Stewart played the role of Elwood P. Dowd once again in a triumphant Broadway revival of Harvey in 1970. This time, Helen Hayes played his sister. Stewart and Hayes reprised their roles for a Hallmark Hall of Fame television production in 1972. Stewart reprised the role for the final time in a 1975 stage revival in London.
The play's author Mary Chase and producer Brock Pemberton were to receive $100,000 per year for ten years against one-third of the film's profits, and the start of the film was contractually delayed until the end of the play's run. Pemberton died in March 1950, before the start of the production.
Mary Chase wanted the audience to see Harvey walking with Elwood at the fadeout, because she did not "want anybody to go out of the theater thinking Elwood is just a lush. He believes in Harvey...and I think the audience ought to believe in Harvey, too."
When speaking with Mrs. Chumley, Elwood describes Harvey as a púca, which is a creature from Irish mythology, and in Celtic as well Nordish myth as well. Referred to as a bringer of either good or bad tidings, a púca can appear in the form of various animals, and sometimes as a human. In most cases, a púca is both friendly and very helpful.
The púca (Irish for spirit/ghost), pooka, phouka, phooka, phooca, puca or púka is primarily a creature of Celtic folklore. Considered to be bringers both of good and bad fortune, they could either help or hinder rural and marine communities. The creatures were said to be shape changers which could take the appearance of black horses, goats and hares. They may also take a human form, which includes various animal features, such as ears or a tail.
The trivia item below may give away important plot points.
When Henry Koster married Peggy Moran in 1941, he promised her he would put her in every movie he made from then on. He did, but it was her statue. Usually it is a sculptured head on a mantelpiece or a piano or desk. In this film, we see the sculptured head of Peggy Moran in the scene (runs for almost 2 minutes without a cut) where Veta Simmons tells Judge Omar Gaffney "Omar, I want you to sue them. They put me in and let Elwood out." In this long take scene, we see the sculptured head of Peggy Moran on the table.