Editing Happy Days (section)

=== {{anchor|Chuck Cunningham Syndrome}} Minor/recurring ===
* Marsha Simms ([[Beatrice Colen]]) (seasons 1–3, 5; 22 episodes) — A [[carhop]] waitress in the first 3 seasons with comic sides and plot development appearances. She returned for a flashback (guest) appearance in the episode "Our Gang".
* Bobby Melner (Harris Kal) (seasons 8–11; 19 episodes) — Friend of Chachi and Joanie seen in episodes after Richie and Ralph left the show. He is a student in Fonzie's auto shop class, as well as in Roger's health class. At one point, he was also on the Jefferson High basketball team, and performed in a band with Joanie and Chachi.
* K.C. Cunningham ([[Crystal Bernard]]) (season 10; 15 episodes) — Howard's niece. She moves in with Howard and Marion after Joanie leaves for Chicago. She left an all-girls boarding school in Texas because it closed down.
* Leopold "Flip" Phillips ([[Billy Warlock]]) (seasons 9–10; 13 episodes) — Roger's rebellious younger brother. He usually wears a shirt cut off over his bellybutton.
* Tommy (Kevin Sullivan) (seasons 8–11; 13 episodes) — Another friend of Chachi and Joanie in episodes after Ron Howard and Don Most left the show. Like Bobby, Tommy is a student in Fonzie's auto shop class, as well as in Roger's health class.
* Heather Pfister ([[Heather O'Rourke]]) (season 10; 12 episodes) — Ashley Pfister's daughter. Initially she does not get along with Fonzie, but gradually learns to accept him as a father figure.
* {{anchor|Chuck Cunningham}} Charles "Chuck" Cunningham ([[Gavan O'Herlihy]], [[Randolph Roberts]]) (seasons 1–2; 11 episodes) — The oldest son of Howard and Marion Cunningham and older brother of Richie and Joanie, Chuck is a college student and basketball player. He is rarely seen and disappears without explanation in season three, never to be seen nor referenced again after season 2's "Fish and Fins". The character's disappearance gave rise to the term "Chuck Cunningham Syndrome", used to describe TV characters that disappear from shows without an in-narrative explanation and are nowhere to be seen or mentioned again.<ref>{{Cite web |last=Abramson |first=Dan |date=June 17, 2010 |title=The 13 Most Ridiculous Sitcom Mysteries Of All Time (PHOTOS) |url=https://www.huffingtonpost.com/2010/04/17/the-most-ridiculous-sitco_n_541532.html |url-status=live |archive-url=https://web.archive.org/web/20170404012114/http://www.huffingtonpost.com/2010/04/17/the-most-ridiculous-sitco_n_541532.html |archive-date=April 4, 2017 |access-date=April 20, 2020 |website=Huffington Post}}</ref> Gavan O'Herlihy played Chuck, but then he asked to leave the series.<ref>{{Cite web |date=December 10, 2017 |title=Meet 'Chuck,' the lost brother from 'Happy Days' |url=http://onmilwaukee.com/ent/articles/gavanoherlihy.html |url-status=live |archive-url=https://web.archive.org/web/20170629151723/https://onmilwaukee.com/ent/articles/gavanoherlihy.html |archive-date=June 29, 2017 |access-date=April 26, 2017}}</ref> He was replaced by Randolph Roberts. In several late-season episodes, Howard and Marion say they are "very proud of our two children", with no on-screen reference to Chuck.
* Eugene Belvin (Denis Mandel) (seasons 8–9; 10 episodes) — Nerdy classmate of Joanie and Chachi, and twin brother of Melvin Belvin. He takes Fonzie's auto shop class and has a crush on Jenny Piccolo. Despite being a general stooge to his classmates at Jefferson High, he frequently tags along with Joanie and Chachi's circle of friends.
* "Bag" Zombroski (Neil J. Schwartz) (seasons 1–4; 9 episodes) — A Jefferson High schoolmate, drummer of Richie's band and a leader of a jacket club called "The Demons".
* Police Officer Kirk / Army Reserve Major Kirk ([[Ed Peck]]) (seasons 3–10; 9 episodes) — Fonzie's nemesis and [[antagonist]], who is eager to demonstrate his inflated sense of authority, and on the watch for delinquents and "[[pinko]]s" (communists). Kirk takes over as acting sheriff following the untimely death of Sheriff Flanaghan.
* Wendy ([[Misty Rowe]]) (season 2; 8 episodes) — A carhop from Arnold's in season two. She is paired with Marsha Simms in 5 episodes.
* Trudy (Tita Bell) (seasons 1–4; 8 episodes) — A Jefferson High classmate, Potsie's and Fonzie's date in various episodes
* Melvin Belvin (Scott Bernstein) (seasons 9–10; 8 episodes) — A nerdy classmate of Joanie and Chachi, and twin brother of Eugene Belvin. Like his brother, Melvin frequently tags along with Joanie's and Chachi's circle of friends.
* Leather Tuscadero ([[Suzi Quatro]]) (seasons 5–6; 7 episodes) — A musician, younger sister of Pinky Tuscadero and a former juvenile delinquent, she forms her own [[girl group]] called "Leather and the Suedes".
* Jennifer Jerome (Lorrie Mahaffey) (seasons 5–6; 6 episodes) — Potsie's steady girlfriend. Mahaffey was [[Anson Williams]]' then wife.
* Laverne De Fazio ([[Penny Marshall]]) and Shirley Feeney ([[Cindy Williams]]) (seasons 3, 6–7; 5 episodes) — Dating interest of Fonzie, Laverne and her friend Shirley appeared prominently in three episodes during season three ("A Date with Fonzie", "Football Frolics", and "Fonzie the Superstar"), which led to the Marshall and Williams starring in the spin-off series ''[[Laverne & Shirley]]''; they also made guest appearances in season six's "Fonzie's Funeral (Part 2)" and season seven's "Shotgun Wedding" (Part 1) (the second part of "Shotgun Wedding" concluded on a [[Crossover (fiction)|crossover]] episode of ''Laverne and Shirley''.)
* Louisa Arcola-Delvecchio ([[Ellen Travolta]]) (seasons 8–11; 5 episodes) — Mother of Chachi Arcola and aunt of Fonzie. She marries Al Delvecchio and they move to Chicago.
* Gloria ([[Linda Purl]]) (season 2; 5 episodes) — Richie's occasional girlfriend in season two.
* Dr. Mickey Malph ([[Alan Oppenheimer]], [[Jack Dodson]]) (season 3–4, 7; 4 episodes) — Ralph's father, an optometrist and, like his son, a self-styled comedian. He briefly separates from his wife Minnie, but apparently resolves the issues with her after a talk with Ralph.
* Raymond "Spike" Fonzarelli (Danny Butch) (seasons 2–4; 4 episodes) — Fonzie's cousin (often referred to as his nephew, but Fonzie explains that he could not be his nephew, as Fonzie was an only child) and his copycat. He goes on a date with Joanie in "Not with My Sister, You Don't" and made only fleeting appearances before the introduction of Chachi.
* Grandma Nussbaum ([[Frances Bay]]) (seasons 3, 9–11: 4 episodes) — Chachi Arcola and Fonzie's grandmother. Grandma Nussbaum was played by [[Lillian Bronson]] in the season 3 episode "Fonzie Moves In".
* Carol "Pinky" Tuscadero ([[Roz Kelly]]) (season 4; 3 episodes) — Former girlfriend of Fonzie and a traveling [[demolition derby]] driver.
* Clarence (Gary Friedkin) (season 10; 3 episodes) — A cook at Arnold's who is referred to several times throughout the show, but never actually seen until the episode "A Woman Not Under the Influence". There, it is revealed that Clarence is a little person.
* Bill "Sticks" Downey ([[John Bailey (American actor) |John Anthony Bailey]]) (season 3; 2 episodes) — Friend of Fonzie, Richie, Potsie, and Ralph and drummer for their band, hence his nickname "Sticks", though he claims he got the nickname because he was skinny.