The story of how an alien ended up in an episode of Happy Days is appropriately bizarre. Creator Garry Marshall's young son had just seen Star Wars and, like many kids in the late 1970s, had become obsessed with space. He even stopped watching his father's show because of the lack of cosmic content.

Marshall told the Archive of American Television, "It's a whole long story. My son stopped watching Happy Days. He was seven. I said. 'Why don't you watch?' He said, 'There's no space people. I like aliens, I like space.'"

Marshall even credited his son for how an alien could be incorporated into the show — make it all a dream!

The young Marshall may have suggested it, but a remarkably similar plotline happened in The Dick Van Dyke Show episode "It May Look Like a Walnut," in which Rob dreamt about an alien (Danny Thomas) after watching a scary movie. The episode was directed by Jerry Paris, who also played the Petries' dentist neighbor. And wouldn't you know it? Fifteen years later, Paris directed "My Favorite Orkan" — Mork's first appearance on Happy Days.

Regardless of how it all came together, once it was decided that an alien should visit 1950s Milwaukee, the next task was to find the right person to play the extraterrestrial.

Many people auditioned for the role. Roger Rees and frequent Mel Brooks collaborator Dom Deluise were considered.

The book I’m Dying Up Here: Heartbreak and High Times in Stand-Up Comedy’s Golden Era details how up-and-coming comedians Richard Lewis and Robin Williams auditioned on the same day. They were told to come up with their best alien voices, but all Lewis could think of was a Danish accent. He knew he had no chance against Williams and even told the producers, "You know, Robin Williams is next. He is Mork, and if he doesn't get this, then you are all crazy."

Sure enough, when his turn came, Williams gave a completely out-of-this-world audition. He stood upside-down!

Garry Marshall told the Television Archive, "He did the whole audition standing on his head and he was great, so he went into Happy Days."

Marshall could see his bet on an unknown comedian pay off immediately. After taping "My Favorite Orkan," the studio audience gave Robin Williams a standing ovation.