Barf in the Urn (Dramatic Irony)
Before Juno has told her dad and Bren that she is pregnant, they confront her at dinner with questions about why she's been acting strange. Her dad asks her about why she's been moving the furniture around (she brought the chair that she got pregnant in to Bleeker's front lawn to sit in while she broke the news). Then, Bren pointedly asks Juno, "Did you barf in my urn?" Bren found some suspicious vomit in a prized urn that she keeps in the front hall. While Juno denies it to Bren's face, the viewer sees a flashback of Juno throwing up in the urn, a sign of morning sickness. Thus, while we know that Juno is pregnant (and lying about vomiting in the urn), her parents have no idea, which creates a dramatic irony.
Bleeker is the Father (Dramatic Irony)
While Juno, Leah, and Juno's parents know that Bleeker is the father of Juno's child, they keep it a secret from the rest of their community. Bleeker's mom already doesn't like Juno, so we get the sense that she would be all the more judgmental and disapproving if it came out that her son had been involved in Juno's pregnancy. Thus, there is a dramatic irony in the fact that we know that Bleeker is the father of Juno's child, but Mrs. Bleeker has no idea.
"I was hoping she was expelled or into hard drugs" (Situational Irony)
After Juno tells Bren and her dad that she is pregnant, they share a comically casual one-on-one conversation about it. While the expected response to a teen pregnancy would be for the parents to be crestfallen, Bren and Mac are surprisingly pragmatic about it. They are still distraught that Juno is pregnant, but they look at it with more of a problem-solving mentality than a defeated one. The most distressed they get is when Bren says, "I was hoping she was expelled or into hard drugs." The irony of this moment is that while the viewer imagines that any parent would be upset if their child was expelled or an addict, Bren is downplaying these problems in relation to teen pregnancy.
Su-Chin's Protest Works (Situational Irony)
When Juno first arrives at the women's clinic to learn more about getting an abortion, she runs into her classmate, Su-Chin, who is protesting abortion outside the clinic. Su-Chin is the sole protestor, and she chants with a pronounced lack of enthusiasm. The two girls talk to each other as classmates, exchanging anecdotes about school; this is itself a kind of irony, the image of a pro-life protestor and a pregnant teen looking to get an abortion talking amicably about school. Juno is a character who is pretty set in her beliefs, and it seems unlikely that she will be dissuaded from procuring "a hasty abortion," as she puts it. However, when Su-Chin offhandedly mentions that her baby has fingernails, Juno pauses. In the waiting room, Juno notices the fingernails of the other patients and has second thoughts about aborting her baby. She leaves the clinic and Su-Chin celebrates the fact that she effectively convinced someone not to get an abortion. The irony is that Juno is a strong-willed and not particularly impressionable person (and she likely hasn't changed her stance on abortions in general), but she is still convinced by her zealous classmate. Not to mention that the decisive detail is the baby's "fingernails," not any of the other arguments that Su-Chin is making. The existence of fingernails doesn't seem like the most persuasive reason not to get an abortion, but for some reason, it haunts Juno.
