The scene starts with Plankton (disguised as a pepper shaker) taking a Krabby Patty but is easily caught by Mr. Krabs. As he is lamenting his failure on a bench in the park, Plankton then hears a woman saying that she can take her baby's milk away from him and he cannot do a thing about it. This makes Plankton realize he will turn Mr. Krabs into a baby.
Plankton then leads Mr. Krabs in a telephone booth by money where he sprays Goo Goo Gas on him, turning Mr. Krabs into a baby but Baby Krabs teeths on Plankton. SpongeBob finds Baby Krabs and takes him, but Plankton accidentally reveals that Baby Krabs is Mr. Krabs and gets arrested, but easily escapes. SpongeBob takes the baby in the Krusty Krab and tries to comfort him with many items, eventually succeeding with a stack of twenties.
Meanwhile, Plankton sprays Baby Krabs and SpongeBob but Mr. Krabs is now an adult and SpongeBob is a baby. Plankton squirts SpongeBob and he is now an adult again. The same thing happens again, and Plankton thinks it was not right. He gets launched out of the Krusty Krab by Mr. Krabs again. Later, Plankton uses a new spray and sprays Mr. Krabs again. However, Mr. Krabs is now elderly, much to Plankton's dismay, thinking it was a baby at first.
Soon, SpongeBob appears out of nowhere and says a speech about caring for Senior Citizens. However, Plankton sprays him as well. Then, he realizes that this was Senior Citizen Spray, but then says that they cannot catch him. SpongeBob and Mr. Krabs then trap Plankton by knitting a net, getting hit one by one by senior citizens.
Plankton then realizes that there is one ingredient that he is missing to turn people into babies.
He then goes to Barg'N-Mart which he buys baby powder and then goes back to complete the experiment. Using Karen as a test subject, it works. He then returns to the Krusty Krab and sprays all the customers, including SpongeBob, Patrick, Squidward, and Mr. Krabs and they never change back to adults again. Plankton is about to get the formula when he gets beaten up by the babies.
Baby SpongeBob then bashes the Goo Goo Gas canister, much to Plankton's dismay. But, Baby SpongeBob accidentally playing with the gas and flies in the air, turning Plankton into a microscopic baby. In the end of the episode, Plankton says "Ahem, Momma's evil little genius needs a diaper!"
Originally, in the scene where Plankton sits on the bench and watches the baby, Plankton would take the babies bottle a few times and then kidnap the baby. The baby's mother would then walk up to the stroller and ask where her baby went. It was heavily implied that Sadie was not going to be the baby's mother.