Both of these shows had long runs on ABC. Happy Days lasted for 10 seasons from 1974-1984, while Family Matters lasted for 8 seasons from 1989-1998. Both shows looked radically different from their Pilot Episodes to their Series Finale. But the similarities do not stop there.
Both Shows Started Off as Spin Offs.
Surprisingly to most viewers. Both shows started off as Spin-Offs to other Sitcoms.
Happy Days started off as a Spin-Off of the comedy anthology show Love American Style which starred Ron Howard(Richie Cunningham), Marion Ross(Marion Cunningham, and Anson Williams(Potsie Webber). With the patriarch Howard Cunningham, Brother Chuck and sister Joanie Cunningham played by different actors.
Family Matters was a Spin-Off of the popular TV series Perfect Strangers as Harriet Winslow(Jo Marie Payton) was a regular character on Perfect Strangers for 2 seasons as the Elevator operator, and Carl Winslow(Reginald VelJohnson) appeared in a few episode of Perfect Strangers.
I wished there was a crossover between Perfect Strangers and Family Matters. Balki in the same room as Steve Urkel would have been a trip! Mark Lynn Baker (Larry Appleton) appeared in one episode of Family Matters, but that was as a different character. Speaking of Urkel........
Had Breakout Characters Who Became The Focal Point of the their shows.
The Fonz Steve Urkel
Arthur Fonzarelli(Henry Winkler) was originally supposed to be a minor character on Happy Days
, and Steve Urkel(Jaleel White) was created for only one episode on Family Matters. But both of these characters got so popular with the fans that the production staffs made them the central characters of their respective shows.
Here are some classic moments from the Fonz and Steve Urkel.
Fonzie Jumping the Shark.
Steve Urkel Doing Some Kung Fu as a Bruce Lee Wannabe. Both of these shows have long "Jumped The Shark" before that.
Relatives who disappeared With No Explanation and Totally Forgotten
Chuck Cunningham Judy Winslow
Both shows had minor sibling characters who just written off and totally forgotten by the writers by the end of each series. Chuck Cunningham(Gavin O Herley) suddenly dissapeared from Happy Days sometime after Season 1, and was written off as Going off to college on a basketball scholarship), because according to Garry Marshall, "we realized that Fonzie was really the 'big brother' character the show needed". In the final episode, Howard comments that he's proud of his "two kids".
And there was no explanation for Judy Winslow's dissapearance. As in real life. Jaime Foxworth(who'd act in porn in a few years) parents wanted a raise, and they writers decided to write her off. Just like Chuck earlier. The later episodes of Family Matters revised the show's history so that Judy never existed and the only two Winslow children were Eddie and Laura.
Another oddly occidental thing between these two shows was that Happy Days and Family Matters were both produced by Miller/Boyett Productions.