| Quote #1
Qs and Ts
Here Casca describes Caesar's theatrical behavior in front of the adoring crowd. After refusing Antony's offer of the crown three times, Caesar faints dramatically, and the crowd loves him all the more for it. Casca suggests that when Caesar appears before his followers, he presents himself as an actor of politics, and the "tag-rag [common, or poor] people" respond to his theatrics like an enthusiastic audience at a playhouse.
| Quote #2
And then he offered it the third
In the last passage, we pointed out how Casca knows that Caesar's dramatic refusal of the crown and fainting spell are just cheap tricks used to curry favor with the "hoot[ing]" and "clap[ing]" crowd. Here Casca continues to describe Caesar's adoring crowd as though they were an audience watching a performance in an Elizabethan playhouse.
In this passage, Shakespeare also seems to be making an inside joke when Casca refers to the loud audience's "stinking breath." Crowded Elizabethan theaters were notoriously smelly places (there being no mouthwash or deodorant at the time). Plus, Elizabethans thought the plague was contracted by breathing in strong odors like bad breath. So when Casca says he was afraid to laugh at Caesar and the crowd because he didn't want to open his "lips" and breath in the "bad air," he's suggesting that 1) the crowd's bad breath might make him faint like Caesar and 2) he might catch the plague. So basically, Casca is bagging on Caesar's rowdy crowd and Shakespeare is bagging on the theatergoers who pay to watch his plays at the same time.
| Quote #3
[...] he loves no plays,
Oh snap! When Julius Caesar wants to insult Cassius, he hurls the worst insult ever – Cassius doesn't like "plays"! (That's Shakespeare the playwright's way of saying that Cassius is a "dangerous" guy.)