- Played by Robin Williams
- Adaptational Heroism: People who see Mork's original appearance on Happy Days after watching this series are likely to be shocked at what a Jerkass he originally was.
- Alien Among Us
- Amusing Alien: Would you expect an alien played by Robin Williams to be anything but funny?
- Beware the Nice Ones: Mork may be a childlike jokester, but he is still an alien with limited telekinetic abilities, and can be a dangerous opponent when angered, as seen in "The Night They Raided Mind-ski's".
- Bizarre Alien Biology: Orkans age backwards, hatch from eggs, and laugh uncontrollably instead of sneezing.
- Blunt Metaphors Trauma: Mork sometimes misunderstands human expressions. Justified somewhat by Mork's alien nature.
- Catch-Phrase: Nanu nanu.
- Fantastic Anthropologist: Mork's job is essentially to observe humans in their natural habitat.
- Humorless Aliens: Mork has difficulty comprehending earth humor.
- Innocent Aliens
- My Species Doth Protest Too Much: Mork is chosen as Earth observer because his constant displays of humor make him out of place on Ork. This alienness only gets worse (and spreads to other areas) as Mork spends more time on Earth.
- Nice Guy: Mork is mostly pacifistic, good with kids, and humorous.
- Papa Wolf: Functional Magic powers + Protectiveness = Big Trouble if you hurt Mearth.
- Retcon: His appearance in Happy Days was said to be an All Just a Dream in that episode. Oddly enough All Just a Dream was a hurdle that another Happy Days spinoff (the long-forgotten Out of the Blue, which featured an angel as its protagonist) had to overcome as well.
- Shed the Family Name: Inverted; Took Mindy's last name when they married in the fourth season. It was either going to be "McConnell" or "Travolta." (Fred told Mindy to shoot for Travolta.)
- Played by Pam Dawber
- Alliterative Name
- Cloudcuckoolander's Minder: Mindy spends a lot of time explaining things to Mork and making sure his strangeness doesn't get him in trouble or reveal his alien origins.
- Daddy's Girl: Mindy and Mr. McConnell are very close. Somewhat justified in that Mindy's mother died when she was little, so her father was the one who raised her.
- First Girl Wins: Mork dated other girls, but Mindy ended up becoming his wife.
- Girl Next Door
- Happily Married: To Mork for most of the last season.
- Interspecies Friendship —> Interspecies Romance.
- Nice Girl: She patiently puts up with Mork's eccentricities.
- Single Woman Seeks Good Man: Or alien.
- Straight Man: Not that she has much choice.
Fred and Cora McConnell
- Played by Conrad Janis and Elizabeth Kerr
- Cool Old Lady: Grandma Cora rides a motorcycle and prefers modern music to the classical which Mindy's father likes. Imagine an old lady who loved both rock music and Mork with his lovable silliness, even after she learned he is an alien.
- Put on a Bus: They were absent for the second season, but Mr. McConnell returned.
- Straight Man: Mindy's father even more so than her.
- Played by Robert Donner
- Cloudcuckoolander: Maybe even more so than Mork.
- Crazy Homeless People
- Funny Schizophrenia: He talks to people who aren't there and holds an ever-changing set of unusual beliefs.
- Played by Tom Poston
- Awful Wedded Life: He wasn't too close to his wife from a one-off comment that he made, although this could be his own fault.
- Cranky Neighbor: most of his character.
- Pet the Dog: Quite literally. While grumpy to most people, he dotes on his dog, Bickie.
- Tsundere: Mr. Bickley is a rare male example. He acts harsh, but every time someone shows him kindness, he becomes adorable.
Remo and Jean DaVinci
- Played by Jay Thomas and Gina Hecht
- Famous-Named Foreigner: The two have the name "DaVinci." Mork even calls Remo "Leonardo's boy" when he first meets him.