Happy Days was a popular sitcom, broadcast on ABC from 1974 until 1984, which focused on life in Milwaukee around the 1950s and 60s. The show's stars, Arthur "The Fonz" Fonzarelli (played by Henry Winkler) and Richie Cunningham (played by Ron Howard) appeared in inserts during Sesame Street season 9. Fonzie and Richie recited the alphabet in one insert and discussed dental hygiene in another. The Fonz also appeared in several solo sketches.
- The show is spoofed as Snappy Days in the Hallmark calendar The Muppets Look at TV with Fozzie taking the role of "The Foz" (Fonzie), Scooter in the Richie role, and The Swedish Chef as Arnold.
- At the beginning of the Sesame Street song "Do the Wash", a boy hits a washing machine to get it to start running, much like the Fonz would hit the jukebox at Arnold's to get it to work.
- In the Muppet Babies episode "I Want My Muppet TV!," Baby Rowlf suggests they watch Happy Dogs.
- In an interview in 100 Greatest TV Characters, Kermit the Frog mistook Fonzie for Fozzie at one point.
- G.W. Bailey played Jack Whitman in the episode "Joanie Busts Out"
- Linda Bove played Allison in the episode "Allison"
- H.B. Haggerty played Bruno in the episode "Nose for News"
- David Ketchum wrote five episodes and played Lt. Col. Binicky in "R.O.T.C.," Coach Pelino in "A Shot in the Dark," and Donald Hedges in three episodes
- Christopher Knight played Binky Hodges in "Be My Valentine" (1978)
- Cheryl Ladd played Cindy Shea in the second season episode "Wish Upon a Star"
- Penny Marshall played Laverne DeFazio in six episodes and the spin-off Laverne & Shirley
- Michael McKean played Lenny in the episode "Fonzie's Funeral Part 2"
- Pat Morita played Arnold (1975-1976, 1982-1983)
- Donny Most played Ralph Malph (1974-1980)
- Tony Randall played a werewolf in the episode "Not with My Sister, You Don't" (1974)
- Cathy Silvers played Jenny Piccolo (1980-1983)
- Frank Welker provided the voice of Mr. Cool on the animated spin-off Fonz and the Happy Days Gang.
- Robin Williams played Mork in the episodes "My Favorite Orkan", "Mork Returns," and the spin-off Mork & Mindy.
- Rita Wilson played Barbara McManus in "Where the Guys Are" (1983) and Roxanne in "A Woman Not Under the Influence" (1982).