What to Expect When Bart's Expecting, it is the nineteenth episode of Season 25.
Bart doesn't like his art class, so when he makes a voodoo doll of his art teacher, she gets pregnant. Fat Tony kidnaps Bart to conceive a thoroughbred racehorse.
As Barney approaches Moe's Tavern, he notices that it is closed for a meeting. A tear falls from Barney's face as he tries to look in the window. Moe is holding a meeting to discuss how sales for mom and pop bars have been low. Moe proposes a superhero themed pub crawl.
Homer and his buddies join in the bar hopping. Homer winds up on his hands and knees in front of his home in the morning, before Bart and Lisa leave on the school bus.
Meanwhile, Bart feels smothered by his art teacher -- who sees something very positive in all of her students' art, which she praises enthusiastically. However, Bart wants to get rid of his teacher.
Bart goes to a voodoo queen, and she sells him some materials to cast a spell on his art teacher -- yet his teacher still shows up to class the next day, surprising Bart. Even though the spell was meant for a stomachache, the art teacher exclaims, "I'm going to have a baby!" Ralph runs outside and announces, "Bart Simpson got a teacher pregnant!" Lisa is in disbelief. Homer picks his son up complaining how embarrassing it is to get a call about Bart's bad news during his arraignment.
When a couple approaches Bart about his baby-making skills, Bart utilizes his voodoo magic. The spell works, and the couple returns to ask Bart if he could they could give their friends -- who are in the same dark place they were -- Bart's name. Bart demands his payment if they want their driver license back.
Homer takes Bart to Moe's to discuss Bart's problems, but Louie and Legs -- Fat Tony's henchmen -- come into the bar and kidnap Homer and Bart. Moe aims a gun at the mobsters because he does not want them to take his paying customers, but Homer reveals that he does not have any cash on him. Moe lets the goons kidnap Homer and Bart.
Homer initially thinks that Fat Tony orders the kidnapping, so that Bart can work his baby magic for Fat Tony, but it turns out that Fat Tony wants Bart's skills to work on his horses. Not only does Fat Tony want his horses to breed, but he demands a male horse. Nonetheless, the stallion turns out to like playing "It's Raining Men" than making babies with the mare. The mare then mates with another stallion named Sudsley Brew-Right and the pregnancy test comes back positive.