The Welcome Back, Kotter flashback episode. The Sweathogs throw Kotter a surprise party before the start of the new semester. During the party, Kotter and the Sweathogs reflect back on all the good times they had over the first two seasons.
Kotter buys Barbarino's share of the Sweathogs' lottery ticket, but Barbarino says he wants no part of it because they never win. When they do win the $1,000 semifinal prize, Barbarino and Kotter disagree on who should get the money.
Kotter refuses to help Barbarino study for his test that would promote him to the eleventh grade. So the Sweathogs make a deal with Kotter. If he helps Barbarino study, they will help Julie and the babies.
The Kotters are looking for a new apartment and having no luck. Juan has an answer to their problem. His Uncle owns a building in a good neighborhood at the right price. The gang helps the Kotters move in and everything seems to be going great...until Moe Epstein tells them that there are no babies allowed.
Woodman writes a novel set during the Civil War era that very closely parallels the Sweathogs, and the Sweathogs are not happy about it. So they write a novel of their own set in outer space and depicting Woodman as the villain.
The Sweathogs' singing group wins the city-wide talent contest semi-finals. Then Barbarino becomes infatuated with one of their finals competitors. When they start dating, it jeopardizes the Sweathogs' chances of winning.
When Woodman's contract for renewal is up, Kotter decides he wants to apply for vice principal. Then he has a dream that he is the king of Buchanan High School and the very old Sweathogs want to oust him from power.
The new girl in Kotter's class declares that she is going to become a Sweathog, but the other Sweathogs strongly oppose her joining their group. So she pulls a stunt to prove her worth which backfires getting the Sweathogs nearly expelled.
The Sweathogs convince Gabe to audition at a local hot spot, never expecting him to succeed, but after Mr. Charnoff a slick agent gets through with him, it's goodbye teacher, hello show biz. First of a two-part episode.
Freddie is prescribed painkillers to treat a nagging injury he suffered playing basketball ... and soon becomes hooked. His friends become concerned about Freddie's increasingly scary behavior, but "Boom-Boom" tries to brush them off - after all, it's just "vitamins." What becomes even more scary is that Horshack blindly believes his friend's explanation, even though it becomes clear that Freddie needs help before something goes horribly wrong.
The Sweathogs sneak out to a strip club and recognize one of the dancers as their former classmate Hotsy Totsy. Shortly after, the Sweathogs, Kotters, and Woodman step in and try to find her a more respectable job.
Carvelli goes to Buchannan High as part of an exchange program and tells the students about his encounter with aliens. Woodman, convinced his story is true, plans to go on the spaceship when it lands in the schoolyard.