One Monday, Mrs. Garrison announces a weeklong project in which the class will be divided into couples and given an egg to look after as a simulation of parenting; if a couple breaks their egg, they receive an automatic F. Stan is worried he will be paired with Wendy, to whom he hasn't spoken since their breakup in "Raisins", only to get a shock when he is paired with Bebe while Wendy is paired with Kyle. Mrs. Garrison's mind is elsewhere, though; she is hoping to patch things up with Mr. Slave after their breakup in "Mr. Garrison's Fancy New Vagina", and shows up at his house with a bunch of flowers - only to find him with Big Gay Al, to whom he is engaged to be married once Colorado legalises same-sex marriages later that week. Seething with jealousy, Mrs. Garrison vows to get the bill overturned and force Mr. Slave to return to her.
Stan is also seething with jealousy, lashing out at Kyle for being paired with Wendy and at Bebe for being paired with him. However, Mrs. Garrison returns from a trip to Denver to persuade the governor to veto the marriage bill with an idea: if she can offer "scientific" proof that same-sex couples are unfit to be parents, it will give the governor an excuse to overturn the bill. The next day, she declares that Kyle is now with Stan, and Wendy is with Bebe. As Bebe has told her of how reckless Stan was with their egg, Wendy becomes worried that the egg she created with Kyle might be in danger and shows up on the Broflovski doorstep to ask to see it, but Kyle assures her the egg will be fine before sending her away. A now fuming Stan takes the egg and storms out, insisting he is just as capable of taking care of it as Kyle. Sure enough, the egg survives the next two days, to Mrs. Garrison's fury; she remains so determined that theirs will be the only egg that breaks that when Cartman inevitably shows up with a smashed egg, she thoroughly confuses him by giving him a replacement, no strings attached.
Deciding desperate measures are called for, Mrs. Garrison hires Jakartha, a sniper, to shoot Stan and Kyle's egg, and makes plans to present the "results" of her study to the governor on Friday. As Stan confronts Kyle over the phone over the perception that he is trying to impress Wendy with his "parenting" skills, Jakartha shoots their egg, but Kyle visits the Marsh house and admits that he didn't trust Stan with the egg, so he gave him a duplicate while he looked after the real one. He admits that he has no interest in Wendy and just wants an A on the project. The now reconciled friends jump in a taxi to the Colorado State House, where Mrs. Garrison is about to announce her "findings" to a crowd of supporters and opponents of the bill. As Stan and Kyle arrive, a furious Mrs. Garrison orders Jakartha to open fire; dozens of bystanders are killed, but the egg stays intact for the exhausted boys to present to Mrs. Garrison. The governor takes this as evidence that same-sex couples are capable parents and signs the marriage bill into law, allowing Big Gay Al and Mr. Slave's wedding to go ahead as planned. As for Stan, he tells Wendy he no longer cares what she thinks of him, and doesn't notice how much this seems to hurt her...
This episode includes examples of:
- Batman Gambit: Kyle knew Stan was too paranoid to trust him with the egg, so he sneakily gave him a fake while holding on to the real one himself.
- Big "NO!": Garrison's reaction to the Governor allowing same-sex marriages.
- Continuity Nod: The episode begins with Mrs. Garrison deciding to patch things up with Mr. Slave after they broke up in "Mr. Garrison's Fancy New Vagina".
- Double Standard: Played with. Mrs. Garrison comes down harder on Stan and Kyle as egg-parents but says nothing of Wendy and Bebe. Paralleling this, during a protest rally, the governor says 'nobody gives a fuck' about lesbians. The reaction is predictable.
- Egg Sitting: Turns out to be the B plot of the episode when Mrs. Garrison's tirade against gay marriage takes center stage.
- Even Evil Has Standards: Subverted. Although Mrs. Garrison claims she's acting against same-sex marriages as a protest about the sanctity of matrimony, it's pretty obvious she's doing it purely to spite Mr. Slave.
- Everyone Has Standards: The gay marriage protesters side with Mrs. Garrison's homophobic speech, until she insists on causing physical harm on gay people through what she called a "fag drag". As one of them put it, they don't hate homosexuals, they just don't think they should be allowed to marry each other.
- Foreshadowing: Heidi and Eric. This episode centers around the students of South Park Elementary being split up into pairs to simulate couples caring for a child. Sure enough, Cartman is paired up with Heidi, and he screws the whole thing up (breaking the egg) before being given a second chance he doesn't deserve (Mrs. Garrison gives him a replacement and doesn't penalize him). It becomes a huge chunk of the Heidi/Eric plot of seasons 20 and 21.
- Hoist by His Own Petard: Mrs. Garrison's plot to make gay marriage illegal ultimately makes it legal in the end.
- Hypocritical Humor: Stan says he wanted to prove to Wendy he was a good egg sitter, only to brush her off at the end when she says he is, though the scene where Stan and Kyle reconcile made him realize he doesn't really care what Wendy thinks of him, may have something to do with it.
- It's All About Me: Mrs. Garrison only wanted gay marriage illegal so Mr. Slave and Big Gay Al couldn't get married.
- Left the Background Music On: When Miss Garrison broke into song during class, everyone stopped what they were doing and looked at her like she had gone more nuts than usual.
- No Kill Like Overkill: The assassin Mrs. Garrison hires to deal with the egg doesn't hesitate to use live ammo and bombs in a crowded place.
- Only Sane Man: Kyle is the only one who treats the egg sitting assignment as what it is, a school project.
- Pet the Dog: Cartman not only admits to breaking his and Heidi's egg, but actually tries to ask Garrison to give him an F and Heidi an A. Even if he did want the grades to be averaged into a C minus through that, this action is far cry from Cartman we've come to know the past few seasons. Despite this Garrison gives him another egg because she can't accept the fact that a male-female couple can't even take care of an egg.
- Reasonable Authority Figure: Played with concerning the governor. He's willing to base his decision concerning the controversial issue of gay marriage on a scientific study, but it's only to absolve himself of any responsibility in the eyes of the voters.
- Sequel Episode: To "Mr. Garrison's Fancy New Vagina" for Mrs. Garrison's story and "Raisins" for Stan's story.
- Serious Business:
- Mrs. Garrison was so determined to make people think a gay couple couldn't handle a child that he enlisted the world's best sniper to shoot Stan and Kyle's egg.
- The kids take the assignment way too seriously as well. Stan thinks Kyle is trying to make himself look good in front of Wendy, Bebe treats Stan like a neglectful father because he's apathetic towards their egg, and Wendy's reaction to losing her egg to Stan and Kyle is to act like a mother losing her actual child. Meanwhile, Kyle is left wondering why everyone is acting so weird.
- Ship Tease: Cartman's action above has led to speculation that Cartman has a thing for Heidi. Fast-forward to the Season 20 episode "The Damned". this is confirmed. In fact, they become a couple in "Wieners Out".
- What a Drag: Mrs. Garrison initially has this in mind for dealing with the gay marriage issue before her fellow protesters suggest just getting the governor to veto the bill.Mrs. Garrison: Come on everybody! Let's get some queers and some trucks and have us a good old-fashioned fag drag!
- What the Hell, Hero?: Kyle calls Stan out for thinking Kyle is trying to steal Wendy when he doesn't really care about her since the break-up.