In Act I, Scene II, Casca tells Brutus and Casca that Antony offered Caesar the Crown. Caesar refused the crown. Brutus is worried the people will choose Caesar. "I do Fear the people Choose Caesar for king" ( I: II: in 75-80). This is important because they don't want him king.
Act IV: Sc I
In Act II, Scene II, Calpurnia had a dream that Caesar got killed. "What mean you, Caesar? Think you walk forth? / You shall not sir out the house today"(II:II: In 5-10). This is important because her dreams come true. He even had the soothsayer cut open a sheep.
Act V: Sc V
In Act III, Scene II, Cassius, Trebonius, Decius, Brutus, Casca stabbed him. "Et tu, Brute? Than fall Caesar" (III:I: In 75-80). This is important because they killed Caesar and thought it was best for Rome and thought he was to ambition. Calpurnia's dream came true.
Theme Act I: Sc II
In Act IV, scene I, Caesar ghost came to Brutus house. He talked to Brutus about the ides of march. "Urge me no more. I shall forget myself; / Have mind upon your health; tempt me no father" (IV:I: In 35-40). This is important because Caesar ghost said he was going to defeat him and Cassius.
In Act V, scene V, Brutus whispers a request first to Clitus and then to Dardanius, he wants one of the men to kill him. They both men refuse to kill him." Farewell, good Strato-Caesar, now be still: / I killed not thee with half so good a will" (V:V: In 45-55). This is important because he lost the war.
In Act I, Scene II, Cassius said that Caesar ambition needs to be looked at. "Caesar's ambition shall be glanced at. / and after this, let me seat him sure; / For we will shake him, or worse days endure"(I:II: In 315-320). This is important because this is when all the conspirators started thinking about killing him. The theme is being to ambitions can be bad and get you killed.