Happy Days is an American television sitcom that aired first-run on the ABC network from January 15, 1974, to July 19, 1984, with a total of 255 half-hour episodes spanning 11 seasons.

The first two seasons of Happy Days focused on the experiences and dilemmas of "innocent teenager" Richie Cunningham, his family, and his high school friends, attempting to "honestly depict a wistful look back at adolescence".

The new format emphasized broad comedy and spotlighted the previously minor character of Fonzie, a "cool" biker and high school dropout.

[2] Following these changes, Happy Days became the number-one program in television in 1976–1977, Fonzie became one of the most merchandised characters of the 1970s, and Henry Winkler became a major star.

However, as the series progressed, Fonzie proved to be a favorite with viewers, and soon more story lines were written to reflect his growing popularity, Winkler was top billed in the opening credits alongside Howard by season 3.

In later seasons, other characters were introduced including Fonzie's young cousin, Chachi Arcola, who became a love interest for Joanie Cunningham.

Happy Days spawned successful television shows Laverne & Shirley and Mork & Mindy as well as three failures: Joanie Loves Chachi, Blansky's Beauties featuring Nancy Walker as Howard's cousin,[6] and Out of the Blue.

The leather jacket worn by Winkler during the series was acquired by the Smithsonian Institution for the permanent collection at the National Museum of American History.

[7] The original, light grey McGregor windbreaker Winkler wore during the first season eventually was thrown into the garbage after ABC relented and allowed the Fonzie character to wear a leather jacket.

In late winter of 1971, Michael Eisner was snowed in at Newark airport where he bumped into Tom Miller, head of development at Paramount.

[20] This unsold pilot was filmed in late 1971 and titled New Family in Town, with Harold Gould in the role of Howard Cunningham, Marion Ross as Marion, Ron Howard as Richie, Anson Williams as Potsie, Ric Carrott as Charles "Chuck" Cunningham, and Susan Neher as Joanie.

In 1972, George Lucas asked to view the pilot to determine if Ron Howard would be suitable to play a teenager in American Graffiti, then in pre-production.

With the movie's success generating a renewed interest in the 1950s era (although the film was set in 1962), TV show creator Garry Marshall and ABC recast the unsold pilot to turn Happy Days into a series.

According to Marshall in an interview, executive producer Tom Miller said while developing the sitcom, "If we do a TV series that takes place in another era, and when it goes into reruns, then it won't look old."

Garry Marshall's earlier television series The Odd Couple had undergone an identical change in production style after its first season in 1970–71.

To accompany this new version, new opening credits were filmed, and the flashing Happy Days logo was reanimated to create an overall "new" feel which incorporated 1980s sensibilities with 1950s nostalgia (although by this time the show was set in 1965).

On April 19, 2011, Happy Days co-stars Erin Moran, Don Most, Marion Ross and Anson Williams, as well as the estate of Tom Bosley (who died in 2010), filed a $10 million breach-of-contract lawsuit against CBS, which owns the show, claiming they had not been paid for merchandising revenues owed under their contracts.

[31] On June 5, 2012, a judge denied a motion filed by CBS to have the case thrown out, which meant it would go to trial on July 17 if the matter was not settled by then.

In 1978, actor Robin Williams made his screen debut during the fifth season of Happy Days, as the character "Mork" in the episode "My Favorite Orkan".

[35] Sought after as a last-minute cast replacement for a departing actor, Williams impressed the producer with his quirky sense of humor when he sat on his head when asked to take a seat for the audition.

[36][37] While portraying Mork on Happy Days, Williams improvised much of his dialogue and physical comedy, speaking in a high, nasal voice, and he made the most of the script.

[39][40][41] In 1985, Jon Hein developed the phrase jumping the shark in response to the season 5 episode "Hollywood: Part 3", written by Fred Fox Jr.,[42] which aired on September 20, 1977.

[43][44][45] The phrase is used to suggest that a creative outlet appears to be making a misguided attempt at generating new attention or publicity for something that is perceived to be once, but no longer, widely popular.

[54] For the second season, CBS features music replacements due to copyright issues, including the theme song "Rock Around the Clock".

[60] The story featured a property developer, and former girlfriend of Fonzie's, called Miss Frost (Rebecca Gibney), wanting to buy the diner and redevelop it.

It starred Craig McLachlan as Fonzie, Max Gillies and Wendy Hughes as Mr. and Mrs. Cunningham, Doug Parkinson as Al, and Jo Beth Taylor as Richie's love interest Laura.

[61][62] The music video for the song "Buddy Holly" (which takes place at Arnold's Drive-in) by Weezer features footage from the series, including clips of Richie, Potsie, Ralph Malph, Joanie, and Fonzie.