Awesome Moments: At the end of "Chicken A La Kotter", Kotter walks out after one too many nasty comments from his boss. He and the Sweathogs take their chicken and leave...but not before Arnold goes back in and puts the head of the chicken costume on the boss's head.
Horshack talking down the suicidal Mary Johnson. In return, she saves his life when he slips and nearly falls off the same ledge she tried to jump from.
When the Sweathogs are afraid Gabe is going to quit as their teacher, they come to his apartment to throw him a potluck dinner to convince him to stay.
When Epstein expresses his desire to become a vet and is told he's not smart enough, he gives Gabe and Julie all of his pets. When one of the hamsters turns out to be pregnant, though, Gabe calls Epstein in to handle the birth and tells him that he's got what it takes to follow his dream.
Julie's character arc in season 4 has her becoming a mentor for the Sweathogs, whom she previously mostly tolerated for Gabe's sake.
Arnold and Mary's relationship is one big heartwarming moment from beginning to end. Highlights include Arnold talking her down from trying to kill herself, the two confessing their love for each other and Mary showing she's gained a lot of pluck and spirit by reassuring Arnold when he panics shortly before their wedding.
Hollywood Pudgy: Judy Borden. The guys call her fat and make fun of her weight, but she's only a tiny bit thicker than the rest of the girls on the show.
Ho Yay: Though the guys were mos definitely straight, they had their share of moments. Most notably Horshack constantly hugging Epstein and calling him "little Juan", or a season 4 episode where Vinnie asked Beau to "look at his body".
Vindicated by Cable: Somewhat. After its original lackluster syndication in the early 80s, the show fell into obscurity in the US until Nick At Nite and TV Land added it to their line-ups in the mid to late 90s. The episode with George Carlin was picked for Malcolm Bondon's Ultimate Fan Hour.
Horshack, especially early on. He puts up with a lot of crap from the other guys and has little to no self-esteem.
Beau, who reveals that he's had a tough life before coming to Bucchanan high school, never really knew the father he talks up so much and feels he has to con people into liking him just to make friends. He ends up playing a prank in order to impress the Sweathogs and keep them as friends, but even that backfires when Mr. Woodman refuses to believe it was him and blames the other guys.