The Mystery Cartoon Character Game, now with 20% more ongoing.

Yeah, I know this one for certain too now, I won't answer unless I need to.

Would this be Randall, from "Monsters Inc." and "Monsters U?"

Verily it would be, SaltyBoot, verily it be. Randall Boggs, specifically, whose arch-nemesis is James P Sullivan. He's the active villain in Monsters, Inc. as opposed to the mastermind, Henry Waternoose. Randall is ultimately sundered by Boo, the little girl he'd routinely frighten to obtain her screams of fear.

I'll award you a new +1, SB, and let you take control of the board.

Ok then, I finally got a character together.

My friend and I found a time capsule in a cave.
I was searching for plutonium rockconium, and he was looking for worms.
We take it to a professor who said it's a message that was sent to another planet.

Can't say I've heard of this one.

Here's three more.

The three of us went to that planet with a robot.
My stopmotion short was shot in stereoscopic 3D.
My name is right in the title.

Hmm, stop-motion made me think of Art Clokey, but both Davey Hanson and Gumby are already on the UCL. Nick Park's A Grand Day Out? No, there was no professor in that one, and Wallace was seeking moon-cheese, not "plutonium rockconium," whatever that is. Of course, since it has plutonium in it, it must be fiercely radioactive; that character had better bring a lead shield to handle the stuff, or even just photograph it.

All right then, last three clues a go.

Though this short was produced in 1953, it was not released until 1960.
My director had animated on George Pal’s Puppetoons.
To expand on clue 5; stereoscopic was also used on the opening title sequence for I Love Lucy.

Sorry, Salty. I checked all the stop motion shorts of the 50's and 60's, and couldn't find it.

Well, this is a surprise. All this time, I thought George Pal was an auteur, and directed / posed / filmed all his projects himself.

Here is a bonus clue. Hopefully this will do it.

My voice actor also did the voice of Boris, from The Rocky and Bullwinkle Show. (It should be noted that the short in question is mentioned on the BMDb for 1955, which is wrong. And it's not mentioned at all on Wiki.)

Obviously, the voice actor in question is Paul Frees, but I still can't find it.

Yes, it is Paul Frees. In the BMDb, this "Adventure" is on 1955. I'm too tired to post the answer and clues. I'll post it tomorrow if no one gets it by lunch time.

Wow, I have my first un-guessed character. I don't know if I should give myself a cookie or a bowl of broccoli.

Anyway, the answer is Sam, from The Adventures of Sam Space.

He and his friend found a time capsule and take it to a professor. They all end up going to another planet.
The short is in stereoscopic 3D, as well as the intro to I Love Lucy.
The director was Paul G. Sprunck, who was the creative artist on The Puppetoon Movie.
Paul Frees did the voices.

Ok, the turn is to anyone who wants it.

Well, I never heard of that one until now. So I'll take the turn, and see if you know this one:

1. I fly alongside the title hero.

2. My name is totally unrelated to both a British spy show, and a team of Marvel superheroes.

3. Given the color of my plumage, I'd have made a good pet for Prince.

Well, out of 231 characters fielded by SaltyBoot as a Mystery Character, this is the first time that one has gone unguessed. The first one can be regarded as a Badge of Honor, in that you've stumped a panel of "experts." After that, though, the unguessed ones lose their luster. Nevertheless, welcome to the Unidentified Mystery Character Club, SB.

Okay, that "purple" clue almost threw me off. I'd watched Hanna-Barbera's Birdman and Avenger on a monochrome set, so I always believed that Avenger was grey. But, no, Avenger is purple (gotta burn up those odd colors somewhere). I forget though: is Avenger a falcon or a hawk? I can never keep those two straight.

Actually, Avenger's an eagle. But at any rate, you got it right, OUB. So take your well-deserved turn. Good job.

Neat-o. Oh, and here's a spot on the List that's little-traveled. I shall remedy that.

1) This character has appeared regularly in an animated television series no longer in production.

2) While his two close associates are human, this character himself is not.

3) Functionally, this character is a close parallel to Ben Grimm of the Fantastic Four: the big, tough guy who does lots of clobberin'.

I quite possibly have the answer now, but I won't post it unless no one gets it by tomorrow afternoon.

Ok, seeing as how no one answered, I'll post it. It can only be Igoo, the rock ape from "The Herculoids." Except that he had three human associates.