Robert Donner is a character actor who, for most of his career, was best known for playing villains.

Apart from a recurring role as Yancy Tucker on The Waltons, Donner was a dependable heavy in Hollywood.

But then in 1978, after 20 years of playing heavies, Donner was cast to guest star in an episode of Mork & Mindy as a colorful character called Exidor.

Exidor is introduced as a street preacher whom Mork befriends. He wore robes and led a cult called "The Friends of Venus," and in Donner’s view:

"He’s a stranger in paradise," Donner told United Press International in 1979. "Mork is from another planet who finds strange things on Earth. Exidor comes from Earth and finds things on his own planet which are strange. They have common ground."

Audience reaction to Exidor was surprising.

The character was so popular that he was brought into 22 episodes, and within a year of his first appearance, ABC was ready to green-light a spin-off show for Donner’s fanatic street preacher.

To say Donner doubted the success of a show based on Exidor would be an understatement.

He told United Press International that "I’ve been pretty outspoken about the suggestion that Exidor should spin off into his own series. I think the idea is crazy."

Donner felt Exidor was simply too weird to carry his own show. He felt the preacher would exhaust any audience that tried to tune in week after week.

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"Exidor is a genuinely far-out character," Donner explained. "He comes into every scene in Mork & Mindy on the ceiling, and you can’t get any higher than that. He’s fine for every third show or so. A little of anyone as strong as Exidor goes a long way. I’m not sure he could hold an audience every week on his own."

In the end, Donner got his way, and Exidor did not have his own spin-off show.

That didn’t mean that Donner was done with the character, though. He was still recognized as Exidor everywhere he went.

"In the more than 20 years I’ve been acting, I’ve never received anything nearly as comparable in public recognition," Donner said.

On Mork & Mindy, Exidor got married off to another wacky character played by Georgia Engel, best known for playing Ted Baxter’s bubbly wife on The Mary Tyler Moore Show.

The premise of Exidor’s show was planned as an offbeat Honeymooners, tracking the adventures of the newlyweds and in Donner’s opinion, that premise would "surpass the insanity yet seen on television."

It wasn’t that he thought Exidor was a bad character, though. Donner loved playing Exidor and saw in him the same qualities he liked playing in the villains he created for decades.

"I am an effective heavy for the same reason that makes Exidor what he is," Donner said. "The common denominator is that a true villain or a true nut believes his cause is just. Exidor doesn’t even know what his cause is, but he believes in it."

So even though he pooh-poohed the spin-off for Exidor, Donner did understand what ABC saw as potential in his most famous character.

"I must admit Exidor is a joy to do," Donner said.