While going through the Baby's clothes that he has outgrown, the kids discover that the nest that the Baby's egg was in has a note, "Property of Gus and Glenda Molehill". Fran remembers that there was a Glenda Molehill in her La Ma's class, and remembers the time there was an earthquake, which caused the eggs to role out of their nest (and the two were unsure if they had the right egg). Earl, who's been abused by Baby so much, decides to call up the other parents to see if they were switched. The Molehills look closer in color to the Baby (the only one of the Sinclairs who is not green), Gus has a personality very similar to the Baby's (along with the same catch phrases), and their baby, Aubrey, is green and wears a shirt like Earl's. Gus takes a liking to Baby, while Earl likes Aubrey (who, in contrast to Baby, is very polite to Earl). Fran, however, remains unconvinced until they get some Absolute Proof. They go to Absolute Proof Labs and do a DNA test, and the results show that Aubrey is indeed the son of the Sinclairs, while Baby belongs to the Molehills.
Earl is the only one who is really happy with Aubrey. Robbie is annoyed that he keeps bleeding, Aubrey feels unsafe with all games they play (even a simple game of "Where's Daddy?"), and Fran can't find the sugar-free tofu teething cookies that Aubrey needs. She is especially unhappy that it's the Baby's birthday and she's not there to spend time with the Baby. Fran soon decides that she wants her baby back, even if science proved otherwise. At the same time, Glenda shows up, appalled at the Baby's behavior, and wants Aubrey back, while Gus still prefers Baby. While the fathers want the other child and the mothers want the child they've always known, Robbie suggests they settle things by seeing Solomon the Great.
Solomon the Great is a judge who uses magic to determine things. He decides to cut Baby in two, but right before he does so, Earl decides that Baby is his child and he doesn't want him cut in two. Solomon still cuts him in half and gives each half to a different family. Since Gus doesn't want half a kid, he gives his half to the Sinclairs and decides to keep Aubrey while he's still in one piece. While Earl is happy to have the whole Baby back, even if it's two halves, Solomon decides that he's shown he's a true parent, and magically puts Baby back into one piece. Afterwards, Earl says that he's still a little bothered by the fact that science said that the Baby is not really their child, which Solomon sees as a request from the audience, and brings in the scientist from the lab, who reveals that there was a mix-up in the lab the whole time.
Includes examples of:
- Bait-and-Switch: When Earl tells the Baby that his first birthday party will include a pony, the Baby acts excited... but rather than have the pony to ride, the pony is to eat.
- Birthday Episode: This episode takes place on Baby's first birthday.
- Borrowed Catchphrase: Gus Molehill says many of Baby's catchphrases, such as "Not the Mama" and "Gotta Love Me".
- Brainy Baby: Despite only being a year old, Aubrey is shown to speak quite sophistically.
- The Complainer Is Always Wrong: Earl is shown to be wrong for being the only Sinclair to accept Aubrey as their real baby.
- Driven to Suicide: Heavily implied that Fran wants to do this when she demands the knife.
- Enfante Terrible: Glenda Molehill can't stand Baby after a single day.
- File Mix Up: At the end of the episode, it is revealed that there was a mix-up with the tests at the laboratory, proving that Baby does in fact, belong to the Sinclairs.
- Foreshadowing: Fran declares that Baby is the Sinclairs' real son, because "a mother knows". Later, Baby calls the doctor who performs the parental tests "a quack". Both turn out to be right.
- Judgment of Solomon: Solomon the Great's method of satisfying the families is to cut Baby Sinclair in two, which Earl and Fran both object to (Fran would rather let the other family take him, but Earl decides he is their child and wants him back), and after Solomon cuts him in half, Gus hates having only half a kid and decides to keep Aubrey only because he's still in one piece. After Earl says that if they chopped Baby into a thousand pieces he'd still keep them all, leading Solomon to decide they are true parents and uses his magic to put Baby back together.
- Lamaze Class: Before Baby was born, Earl and Fran attended a lamaze class. However, since dinosaurs are born from eggs, the classes are essentially useless. What's more, the administrator says there's no refund.Earl: I spent two hundred bucks for this and my butt is falling asleep!
- Meaningful Name: Solomon the Great is named after Judge Solomon.
- No Celebrities Were Harmed: Robbie watches a music video by Lyzard Skyzard.
- Noodle Incident: Apparently, before Baby was born, there was an earthquake at lamaze class, causing the Sinclairs' and Molehills' to get each others' nests, and momentarily think they got each others' kids.
- No Sympathy: Earl is so delighted by Aubrey's good behavior that he's completely unsympathetic to the anguish Fran goes through after Baby is taken by the Molehills.
- Only One Finds It Fun: When tests at the laboratory reveal Aubrey to belong to the Sinclairs and Baby to belong to the Molehills, Robbie and Charlene both find Aubrey's needy and hypochondriacal personality annoying, while Fran doesn't accept him as her son. Earl is the only member of the Sinclair family who likes having Aubrey as a son, because Aubrey isn't physically abusive to him.
- Red Herring: Aubrey being green with a shirt like Earl is ultimately this, as is Gus Molehill's usage of Baby Sinclair's catchphrases, such as "Gotta love me", "Not the mama" and "Again".
- Special Guest: Jason Alexander as Gus Molehill.
- Status Quo Is God: The Sinclairs get their baby back, and they learn that the labs mixed-up the test results.
- Switched at Birth: Both the title and premise of this episode.
- We Want Our Jerk Back: Played with. Earl is ecstatic to have a son that isn't physically abusive to him, but Robbie and Charlene find his needy and hypochondriacal personality annoying, and Fran doesn't accept him as her son.
- Would Hurt a Child: the lab tests performed on the babies are exceedingly violent and cruel, involving them being electrocuted and submerged in water. Baby enjoys these tests, but Aubrey does not.