The Godfather
Clemenza starts off as one of Don Vito Corleone's caporegimes and oldest friends, as well as the godfather of his eldest son, Sonny. He has a reputation as a superb judge of talent; his crew produced no fewer than five future capos — Sonny, Frank Pentangeli, Rocco Lampone, Al Neri and Joey Zasa.
He is a supporting character in the story, but a few of his actions are important to the plot. For example, he is ordered by Don Corleone, via consigliere Tom Hagen, to handle the beating of two teenage boys who assaulted the daughter of undertaker Amerigo Bonasera, Mrs. Corleone's god-daughter, and escaped punishment for it. Clemenza then assigns his "button man" Paulie Gatto to the job, who then recruits two former professional boxers turned Corleone Family loan enforcers to assist. (A deleted scene from the film depicts Gatto delivering the reprimand.)
When the family finds out that Gatto helped Virgil Sollozzo and the Tattaglia Family set up Vito to be assassinated, Sonny orders Clemenza to kill him. Clemenza considers Gatto's actions to be a personal insult, having personally groomed him, and is more than happy to have him taken out. According to the novel, Sonny Corleone initially suspects Clemenza of being a part of the conspiracy, but Clemenza is eventually cleared. He decides to use Lampone, then an associate, on the hit to give him a chance to "make his bones." In order to lull Gatto into a false sense of security, Clemenza and Lampone drive around in a car with him for at least two days (backing out of the drive, Clemenza asks Gatto to "mind the kids" - it is not specified whether or not these are Clemenza's children) looking for good sites where Corleone men can hide out on mattresses in the imminent war. After Lampone kills Gatto, Clemenza - who has left the car to relieve himself - utters (to Lampone) his most famous line in the movie: "Leave the gun. Take the cannoli."
When Vito's youngest son, Michael, offers to kill both Sollozzo and Police Captain McCluskey, who is on Sollozzo's payroll, Clemenza teaches him how to use the gun and instructs him on how to act in order to allay Sollozzo's suspicions and what to do after the killing. The plan succeeds, and while Michael hides out in Sicily, Clemenza prepares for an all-out war against the remaining four families. The war ultimately claims Sonny's life, and Vito re-assumes leadership following the assassination. Upon his return to New York, Michael is appointed head of the family, but Clemenza and fellow caporegime Salvatore Tessio, unsatisfied with the way things are going, request that they be given permission to break off from the Corleone family to start their own families. Michael accepts, only after their business is over. When Michael is again targeted for assassination by Don Emilio Barzini, who was behind Sonny's murder, Clemenza is initially one of the two primary suspects of being the Corleone family traitor, but it is later revealed to be Tessio, who is killed for his treachery. Clemenza, on Michael's orders, personally murders both Don Victor Stracci and Carlo Rizzi, Michael's brother-in-law, who conspired with Barzini to kill Sonny. He is last seen in the film greeting Michael as "Don Corleone" and kissing Michael's hand.
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