- Zero Mostel - Max Bialystock
- Gene Wilder - Leo Bloom
- Kenneth Mars - Franz Liebkind
- Dick Shawn - Lorenzo St. DuBois
- William Hickey - Drunk
- Zale Kessler - Jason Green
- Arthur Rubin - Jack Lepidus
- Michael Davis - Lead Stormtrooper
- Lee Meredith - Ulla
- Christopher Hewett - Roger DeBris
- Andréas Voutsinas - Carmen Ghia
- Estelle Winwood - Hold-Me, Touch-Me
- Barney Martin - Goerring
Max Bialystock is a washed-up, aging, and also fraud and corruptible greedy Broadway producer who ekes out a living romancing lascivious wealthy elderly women in exchange for money for his next play. Accountant Leopold "Leo" Bloom arrives at Max's office to do his books and discovers there is a $2,000 overcharge in the accounts of Max's last play because he raised more money than he could repay by selling more than 100% of the shares in the potential profits. Max persuades Leo to hide the relatively minor fraud, and, while shuffling numbers, Leo has a revelation: a producer could make a lot more money with a flop than a hit. Max immediately puts this scheme into action. They will over-sell shares again, but on a much larger scale, and produce a play that will close on opening night. No one audits the books of a play presumed to have lost money, thus avoiding a pay-out and leaving the duo free to flee to Rio de Janeiro with the profits. Leo is afraid such a criminal venture will fail and they will go to prison, but Max eventually convinces him that his drab existence is no better than prison.
After reading many bad plays, the partners find the obvious choice for their scheme: Springtime for Hitler: A Gay Romp with Adolf and Eva at Berchtesgaden. It is "a love letter to Hitler" written in total sincerity by deranged ex-Nazi Franz Liebkind. Max and Leo persuade Liebkind to sign over the stage rights, telling him they want to show the world "the Hitler you loved, the Hitler you knew, the Hitler with a song in his heart." To guarantee that the show is a flop, they hire Roger De Bris, a director whose plays "close on the first day of rehearsal". The part of Hitler goes to a charismatic but only semi-coherent, flower power hippie named Lorenzo St. DuBois, a.k.a. L.S.D., who can barely remember his own name and had mistakenly wandered into their theater during the casting call. After Max sells 25,000% of the play to his regular investors (dozens of lustful little old ladies), they are sure to be on their way to Rio.
The result of all of this is a cheerfully upbeat and utterly tasteless musical play purporting to be about the happy home life of a brutal dictator. It opens with a lavish production of the title song, "Springtime For Hitler", which celebrates Nazi Germany crushing Europe ("Springtime for Hitler and Germany/Winter for Poland and France"). After seeing the audience's dumbfounded disbelief, Max and Leo, confident that the play will be a flop, go to a bar across the street to celebrate and get drunk. Unbeknownst to them, their attempt backfires as, after initial dumbfounded disbelief, the audience finds L.S.D.'s beatnik-like portrayal (and constant ad-libbing) to be hilarious and misinterpret the production as a satire. During intermission, some members of the audience come to the bar at which Max and Leo are drinking and rave about the play, much to Max and Leo's horror. The two decide to return to the theater after intermission to hear what the rest of the audience has to say, which echoes what the others already have said. Meanwhile, L.S.D.'s portrayal of Hitler enrages and humiliates Franz, who, after going behind the stage, untying the cable holding up the curtain and rushing out on stage, confronts the audience and rants about the treatment of his beloved play. However, someone behind the curtain manages to knock him out and remove him from the stage, and the audience assumes that Franz's rant was part of the act. Springtime For Hitler is declared a smash hit, which means, of course, the investors will be expecting a larger financial return than can be paid out.
As the stunned partners turn on each other, a gun-wielding Franz confronts them, who accuses them of breaking the "Siegfried Oath". After failing to shoot Max and Leo, Franz tries to shoot himself but has run out of bullets. Leo comforts Franz while Max tries to convince Franz to kill the actors, but Leo intervenes. After a reconciliation, the three band together and decide to blow up the theater to end the production but are injured, arrested, tried, and found "incredibly guilty" by the jury. Before sentencing, Leo makes an impassioned statement praising Max (while also referring to him as "the most selfish man I have ever met in my life"), and Max tells the judge that they have learned their lesson and will not do what they did again.
In prison, Max, Leo, and Franz go back to producing a new play in prison called Prisoners of Love. However, Leo continues the same old scam of overselling shares of the play to the other prisoners (20%-30%) and even to the warden (50%).
- "Flying Down to Rio" - Max
- "America the Beautiful" - Franz
- "Deutschland, Über Alles" - Franz
- "A Wandering Mistrel, I" - Jack Lapidus
- "Beautiful Dreamer" - Auditioning Hitler
- "Haben Sie Gehurt Das Deutsche Band" - Jason Green
- "Love Power" - L.S.D.
- "Springtime for Hitler" - Peasants and Stormtroopers
- "Hitler's Campaign" - L.S.D.
- "By the Light of the Silvery Moon" - Max, Leo and Drunk
- "Yankee Doodle Dandy" - Franz
- "Prisoners of Love" - Prisoners