Tools of Characterization
Shylock is very particular in the play about setting himself up as different from the Christians. There's ample joking about pork-eaters from Lancelot, but Shylock really seems to hold it as a point of pride and separation between himself and the Christians that he won't eat swine, which Jews consider unclean. When Bassanio first tries to convince Shylock to give him the loan, he invites him to dinner. Shylock makes a big point of saying that he draws a line at eating, drinking, and praying with Christians. It's ironic that the night he loses Jessica to Lorenzo, it's because he's finally accepted a dinner invitation from...yes, you got it, some Christians. He goes to "feed his own hatred" by scorning the excess and frippery of what he calls "the prodigal Christian" (alluding to the wasteful prodigal son of the Bible).
While Shylock's avoidance of pork begins as a point of pride, it becomes a jest throughout the play, as Lancelot teases that Jessica's conversion will drive up the price of pork. In the end, as Shylock undergoes a forced conversion, the issue of pork is a reminder that not only his avowed religion will change, but also the cultural habits he held so dear. This is more than a paper conversion, it's a disavowal of the lifestyle he spent a lifetime being proud of.
Cross-dressing is a pretty common occurrence in the play, as Jessica, Nerissa, and Portia all end up in men's clothes at some time or another. Their cross-dressing allows each of them to carry out some role that they would be unable to do as women. Jessica's disguise as a boy frees her from her father's oppressive house, and Portia and Nerissa are given the freedom to actually contribute to Antonio's trial as soon as they don the man-gear. As women, Portia and Nerissa can only pray and give money to the cause, but, once they are given the freedom of men, they single-handedly save Antonio and put their husbands in their places with the ring trick. There's definitely an element of mischief present in the cross-dressing, too – the girls know they're going to get away with things they wouldn't normally be able to do, and they're inspired to the kind of bad behavior it seems boys get to revel in all the time.
Speech and Dialogue: Repetition and Rhetoric
Repetition operates in the play most effectively in the character of Shylock, especially when he is angry. Often those "Christian intercessors" (3.2) try to talk and reason with Shylock, but their points lack substance. Portia's entire speech on the nature of mercy in the courtroom asserts that Shylock should be merciful because it's a good thing to be. The Christians aren't particularly great at reasoning, and they have a habit of being overly verbose and grandiose in their speech, as when Bassanio tells Antonio the long arrow story and all he really means is "Can I get some money?"
Shylock, by contrast, says exactly what he needs to say. His terse speeches let the Christians know that not only is he totally convinced about what he's saying, but he won't be moved by any of their florid speeches. When Shylock brings the jailer to Antonio in Act III, Scene 3, Antonio keeps trying to cut in with reason. Shylock deflects him by simply repeating some iteration of "I'll have my bond" about five times in fewer than fifteen lines. In court, while Portia talks about mercy, Shylock sticks to his guns by repeating that he'll have justice and nothing else. This comes back to bite him later when Portia delivers her crushing legal judgment. She seems pretty spiteful when she says "For, as thou urgest justice, be assur'd / Thou shalt have justice, more than thou desir'st" (4.1.329-330). We might attribute her irritation to Shylock's insistent repetition, which showed her diatribe about mercy to be completely irrelevant to the issue at hand.
Shylock's most important repetition comes with the "I am a Jew" speech of Act 3, Scene 1. He repeats questions and answers in an almost hypnotic way, and he leads the listener to his conclusion by drawing them along with a building series of questions. This is almost the opposite of the cryptic manner of Portia's caskets, or the flowery manner of Bassanio's wooing. The listener follows because of his simple, straightforward speech, and the content is made all the more striking because of its poetic clarity.