Much of the scene where Rupert (Robert De Niro) shows up at Jerry's house was improvised. Kim Chan improvised his lines when Jonno calls Jerry. The part where Jonno has troubling opening the front door was not planned. Chan really could not open the door, and Jerry Lewis improvised his reaction.
Martin Scorsese said later that making this film was an "unsettling" experience, in part because of the embarrassing, bitter material of the script. Scorsese said that he and Robert De Niro may have not worked together again for seven years because making The King of Comedy (1982) was so emotionally gruelling.
When Jerry Langford is walking down the street, he is stopped by a woman talking on the telephone. When Jerry refuses to talk to someone on the phone, the lady says, "I hope you get cancer". This incident actually happened to Jerry Lewis. According to Scorsese, Lewis directed this segment himself.
Robert De Niro used anti-Semitic remarks to anger Jerry Lewis while filming the scene where Rupert Pupkin crashes Jerry Langford's country home. Lewis, who had never worked with method actors, was shocked and appalled, but delivered an extremely credible performance.
Jerry Lewis played a character with the same first name as his own. Jerry Langford was originally named Bobby Langford in the script. But Lewis suggested that the character be named after him, so that they could film reactions from real passersby who recognized him. None of the other people in that scene were actors or actresses except for the cabbie, and the woman on the payphone.
Jerry Lewis found Martin Scorsese's working method initially frustrating, as he was made to wait around for the first three days of shooting. Lewis told Scorsese that he was a professional and was going to get paid for all the time he was made to wait, and that if Scorsese wasn't going to use him, then he could tell him that he wasn't needed.
The talk show segments were filmed on videotape (like a real talk show) and later transferred to film. An unedited version of Jerry's monologue in its original video format can be seen as part of the DVD's special features.
DIRECTOR_CAMEO(Martin Scorsese): Man in van, as Jerry Langford is walking across the street and is greeted by a woman at a phone booth, where she wants him to talk to her nephew Morris, Scorsese can be seen in the driver's side of a green van.
Liza Minnelli filmed a scene where she played herself on Jerry Langford's talk show and sang "New York, New York," but it didn't make the final cut. Minnelli only appears in the finished film as a life-sized cardboard cutout, a guest on Rupert Pupkin's basement talk show. Her name still appears in the closing credits.
Robert De Niro wrote Martin Scorsese a letter before filming expressing his reluctance to the casting of Jerry Lewis as Langford, feeling Lewis might be tempted to ham it up, and not be able to deliver a believable dramatic performance. Martin Scorsese argued that Lewis' own experience as an old-school Borscht Belt and Catskills-based comedian, and the pathos that lied within his manic film comic persona would help him understand and portray the angst of Jerry Langford. Scorsese ultimately proved to be correct, as Lewis received plenty of accolades and critical acclaim for his remarkably understated, restrained performance.
In the original script, when Rupert and Rita meet in the diner, there is a stranger sitting behind Rupert who flirts with Rita. Later, this stranger propositions her successfully. Although he is glimpsed in the film, it is not clear what he is doing. Another change is that in the script, when Rupert is being interviewed by the authorities who are looking for Jerry, Rupert is beaten, this does not happen in the film.
In his monologue on the Jerry Langford show, Rupert Pupkin says that he is from Clifton, New Jersey. This is possibly an allusion to Andy Kaufman's abusive comedian persona, Tony Clifton, whom Pupkin resembles with similar hair, mustache and cheap blue suits.
Martin Scorsese had suffered from poor health both before and during the film's production. He had previously worked on three films close together, and not long afterward, found himself hospitalized due to exhaustion and pneumonia. He had not recovered when shooting began. The intensive filming schedule meant Scorsese could spend the remainder of his time recuperating.
At the time of release, the pride and joy gag would have been universally recognized by American audiences because these two products were heavily advertised. Joy is a brand of dishwashing soap and Pride was a furniture polish. Since Pride has been off the market for many years and Joy no longer does as much advertising, this joke may be lost on audiences too young to remember these products.