- Hilarious in Hindsight: John Travolta would later spend a whole movie with a rubber hose up his nose.
- In one episode, Freddie gives a Jive Turkey-laden speech about how he'd run things if he were president, talking a lot about change. Hmm, sound familiar? Also doubles as Heartwarming in Hindsight.
- 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 most 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". Arnold and Vinnie also go way back to their toddler years, and Arnold sometimes acts as a Morality Pet to the normally clueless and self-centered Vinnie.
- In real life, actor Ron Palillo was gay, being involved in a same-sex relationship with his partner Joseph Gramm from 1971 to 2012 when Palillo died of a heart attack.
- Retroactive Recognition:
- John Travolta as Vinnie Barbarino
- Ron Palillo had a later career in voicing animated characters: Sgt. Squealy in Laverne and Shirley Join the Army; Rubik from Rubik, the Amazing Cube; Ordinary Guy from Darkwing Duck, among other roles.
- James Woods as a rival teacher of Kotter's
- Marcia Strassman (Julie Kotter) is also best known for playing Diane Szalinski in Honey, I Shrunk the Kids.
- Robert Hegyes (Juan Epstein) is also best known for playing Det. Manny Esposito on Cagney & Lacey.
- Debralee Scott had a recurring role as Rosalie "Hotsie" Totsie. Scott is best known for playing Cathy Shumway on Mary Hartman, Mary Hartman.
- Charles Fleischer also had a recurring role as Carvelli, before becoming Roger Rabbit.
- Bob Claver directed 20 episodes. Claver is best known for co-creating Captain Kangaroo.
- James Komack directed three episodes, wrote an episode, and served as executive producer. Komack is best known as creator and executive producer of Chico and the Man.
- Bill Persky directed an episode. Persky is best known as co-creator and co-executive producer of That Girl.
- Mel Stuart also directed an episode and also wrote an episode. Stuart is best known for directing Willy Wonka & the Chocolate Factory.
- Al Schwartz also directed an episode. Schwartz is best known for creating Dotto.
- Eric Cohen wrote 16 episodes. Cohen is best known as co-creator and executive producer of So Little Time.
- Earl Barret wrote six episodes. Barret is best known as co-developer and co-executive producer of Too Close for Comfort.
- Royce D. Applegate wrote an episode. Applegate is best known for playing Chief Manilow Crocker on SeaQuest DSV.
- William Bickley and Michael Warren also wrote an episode. Both are best known as creators and executive producers of Family Matters and Step by Step.
- Pat Proft also wrote an episode. Proft is best known for co-writing Police Academy.
- Garry Shandling also wrote an episode. Shandling is best known as co-creator, executive producer, and star of It's Garry Shandling's Show and The Larry Sanders Show.
- The Woobie:
- 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 Buchanan 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.
YMMV / Welcome Back, Kotter