The Ghostbusters, accompanied by Slimer, are apprehending a ghost in a room full of clocks after receiving a call from a police officer. However, the ghost creates a surge of energy, which combines with the proton beams, and the combined energy hits Egon. They fail to catch the ghost and Egon is knocked unconscious, but thankfully it flies out of the building and he wakes up. They leave, but the clocks are covered in green goo and running backwards.
The next morning, Slimer and Ray serve pancakes, while Louis informs the Ghostbusters (except Egon) that expensive have gone up while profits have fallen. He then reveals that he invited some investors over, but the Ghostbusters are not impressed. Egon enters, wearing a different outfit and listening to music, and the others ask why he is wearing the outfit. He doesn't answer, but instead offers them to listen to the "rap Shakespeare" he's listening to and shows off a machine he made to remove pimples. When Peter isn't impressed by the machine and instead jokes about it, Egon gets salty and leaves, confusing the rest of them.
Two investors come over, but Egon starts shooting water balloons at them with a gun he made from the top of the firepole and Slimer accidentally slimes them, causing them to angrily leave. Egon, who appears to have shrunk, starts roller-skating around the place and Ray suggests that the accident the previous night is making Egon age backwards.
They decide to search for the ghost and, as if on cue, they get a call involving a ghost haunting a clock. They chase after it (while Egon, who has turned into a younger child, whines about several things, including being thirsty and wanting the car to go faster). They find the ghost, who is trying to stop time, but again they fail to catch it, and Egon turns into a toddler.
They go home and Ray determines that if they don't turn Egon back to normal by midnight, he will disappear. Meanwhile, Egon has turned into a baby, and while his friends are mulling over what to do, he soils his diaper. The other guys and Slimer change him (after a bit of difficulty) and take a group photo. Then, they get another call about the clock ghost, so they head off, leaving Egon in the care of Slimer.
While Slimer tries to cheer up a sad Egon, the rest chase down the clock ghost. They go to the firehouse to retrieve Egon so they can bring him back to normal, only to find he has built a ladder and escaped out the window. He falls, but Slimer catches him, only for the clock ghost to steal Egon.
The others pursue the clock ghost and trap him, and Egon, who remembers nothing that happened, returns to normal. The next day, Egon doesn't believe his friends' recount of the episode, but he manages to cheer up a crying baby by babbling to it.
This episode provides examples of:
- Baby Talk:
- When Egon is a baby, he at one point says, "Dirty di-di".
- When Slimer is explaining that Egon's asleep, he uses the word "beddy-byes".
- Bizarre Taste in Food: When Egon reverts to a teenager, he pours orange juice on his pancakes.
- Bratty Half-Pint: When he's turned into a young boy (about six years old), Egon whines about the car not going fast enough and being thirsty, and he gets very grabby about his proton pack.
- Cassandra Truth: At the end, Egon doesn't believe the others when they tell him he turned into a baby.
- Covered in Gunge: Slimer ends up getting ectoplasm on the investors.
- Death By De Aging: Defied. Egon's friends have to reverse the change before midnight, lest he disappear.
- The Diaper Change: When Egon turns into a baby, the rest need to change him and they end up wrapping him up like a mummy.
- Early Personality Signs: As a preteen, Egon builds a sophisticated machine (albeit a water balloon launcher).
- Like a Surgeon: When the guys change baby Egon's diaper, they wear scrubs, and Peter and Ray call out tersely for items the way a surgeon would.
- Lost Food Grievance: Baby Egon cries when Slimer drinks all his formula.
- Merlin Sickness: The main conflict of the episode is that Egon is growing younger and younger.
- Not So Stoic: Egon is notably less stone-faced in his younger incarnations:
- As a teenager, he dances, uses words like "dude" and snaps at Peter.
- As a preteen, he behaves in a very playful way, firing water guns and roller-skating.
- As a young child, he's whiny and at one point exclaims, "Let's bust that sucker!".
- As a baby, he laughs and cries.
- Nursery Rhyme: Slimer tries to cheer baby Egon up by singing "This Old Man".
- Powder Gag: Egon is aging backwards, and once he becomes a baby, the rest have to change his diaper. When Slimer tries to powder him, he gets powder everywhere, and everyone (except baby Egon himself) starts coughing and sneezing, with Slimer even sneezing so hard, he launches himself into the trash.
- Say My Name: Slimer yells, "EGON!" when Egon is knocked out.
- Shout-Out: The title is inspired by the title of Three Men and a Baby.
- Snarking Thanks: As a teenager, Egon insincerely "thanks" Peter for not understanding him.
- Teen Genius: As a teen, Egon invents a high-tech pimple-removing device.
- Tempting Fate: Louis calls the Ghostbusters mature, only for Egon, now a preteen, to start firing water balloons at them.
- Took a Level in Kindness: Implied. When Egon is a teenager, he snaps at Peter, which he doesn't do now, implying he went through a rude phase as a teenager. Also, when he turns into a kid of around six years, he's a bit of a Bratty Half-Pint.
- Water Guns and Balloons: When Egon turns into a preteen, he invents a water balloon launcher and starts shooting water balloons at the investors.
