Written by Joe Glauberg and series creator Garry Marshall and directed by Jerry Paris, the episode originally aired on ABC on February 28, 1978.
It is notable for introducing Robin Williams to a larger audience; the actor's popular appearance in this episode led to the spin-off series Mork & Mindy, which was based on his character.
[1] At Arnold's Drive-In, Richie remarks that he thinks he saw a flying saucer, but Fonzie, Ralph, Potsie and Chachi don't believe him.
He heads upstairs to pack and tells Mork to make himself comfortable; the spaceman does, watching The Andy Griffith Show on the family TV set.
Again, the doorbell rings and Richie answers it; at the door is a man who resembles Mork, except he is speaking with a Southern accent and merely asking for directions.
(In an ending shot for the summer 1978 rerun, it turns out the man really is Mork, and he made it seem like the entire event was a dream.
Producer Garry Marshall watched Star Wars with his son, who asked him for a Happy Days episode with an alien in it.
The cast considered the original script unusable, and production proved so difficult that the intended actor for the alien, Roger Rees, abruptly quit.
The cast was astounded on set at Williams effortlessly improvising the whole Mork persona on the spot and thus creating a highly amusing character that transcended the poor script.
This included the series' writers who came on set to take notes of Williams' gags, and network executives who heard of this new performer's outstanding talent.
The executives were so impressed that a contract for Williams to star in his own series, Mork and Mindy, was prepared and signed four days later.