The Mystery Cartoon Character Game, ongoing.

Indeed. It's Professor Calvin Q Calculus from "The Hole Idea."
1. Self- explanitory.
2. His wife, Gertrude, does not share the same enthusiasm as Calculus does about his inventions.
3. In the end of the short, while his wife is complaining (yet again) Calculus throws one down one of his holes on the floor for Gertrude to fall down into. "My, that was a deep one." remarks Calculus. Suddenly, the hole blazes with fire, and out pops the Devil himself with Gertrude. "Isn't it bad enough down there without her?" he enquires.

Wonderful, always liked him. Now for a character not seen in a while ... aha, found one.

1) This is the title character of a regularly televised animated series, based upon a classic work of literature.

2) Being a "good guy," this character has a sidekick; a darned helpful one, too.

3) Justice, propriety and decency mean a lot to this character. Pity that he has such a poor method of effecting them.

I have an idea, but I'll see if someone else can figure it out.

I only found one series that matches clue 1, but nothing comes close to the other 2 clues.

Okay, let's tighten the focus and name this puppy.

4) Italy saw this cartoon before the United States did. Understandable, since an Italian broadcaster developed and funded the idea.

5) The title character is patently ridiculous, hopelessly unqualified for his job. His horse shows more competence than him.

6) This character also has a speech impediment; not surprising, since his voice is provided by none other than Frank Welker.

Don Coyote, from The Adventures of Don Coyote and Sancho Panda?

Precisactly, this is the well-meaning but poorly-prepared knight errant Don Coyote, very loosely derived from the book by Miguel des Cervantes. This was jointly produced by RAI Radiotelevisione Italiana and Hanna-Barbera Studios. This earns PeterHale another +1 and control of the board.

Here is one not yet on the list...

1) I've been animated in 3 series by different studios - once for the big screen and twice for the small.
2) I've also appeared in TV commercials, and featured in two TV Specials.
3) I have a friend with a weight problem.

Sorry, Pete. I just don't have it. Someone else has seen this guy for sure.

Perhaps this is Popeye the Sailor Man, first adapted from the comics by Fleischer Studios, then by Famous Studios, then later by Hanna-Barbera Studios. The friend with the weight problem would be J Wellingtom Wimpy, corpulent mooch nonpareil.

Um, OUB, if I remember correctly, Popeye's already on the list.

Of course. But rather than a mindless "I dunno" response, I figure to throw out bricks. That way, the questioner can see where my mind is going with the clues given. The cowboy who knows know a calf thinks will have little trouble roping a stray dogie.

A stimulating answer, although, as OUB admits, one that has already been guessed. So let's see if we can rope that dogie!

4) I started out as a weekly panel.
5) My anime series was not a great success - despite its fidelity to the comics.
6) My creator has the same name as a cartoon character first introduced by one of my voice artists.

Near as I can figure, it's probably Keith from "Voltron."

Not Keith Kolgane. If it's any help, OUB's guess was a bit closer to the mark.

OK - the last 3 clues...

7) After my first series I was replaced by the studio's own creation.
8) My last series reprised my earlier theme song.
9) Well - a kite needs a tail... and you have to write with something... and that clock...

All those clues, and I still can't figure it out. Hopefully, one of the others will get it.

Unfortunately, it won't be me. I'm stuck on this.

Intriguing: a comic strip likely from newspapers was made into an anime cartoon to lukewarm success. And I can almost picture a character shrugging off losing his tail to complete a kite, but somehow it just won't focus. I would say Warner Brothers' Sylvester the Cat, but he's already used, and I can't picture an anime studio getting the rights to him. Dang, all this thinking's making my head hurt.

Oh dear - when OUB posited Popeye a few posts back I was sure it would go quickly: he was so in the right direction! Perhaps I should give one final important clue which I had withheld - I'm female.