He was. He struck a match on Skinner’s “No Smoking” sign.
Worf on ST: DS9.
Does Radical Edward on Cowboy Bebop count?
Nope. I think it would be hard for any anime character to meet the OP’s criteria, since either the length and story of an anime has been established prior to being created, or its based off of a manga and draw its characters from there.
Minority of two. Don’t forget Jenny Calendar, Principal Snyder, and Faith…
I assume you’re joking, but in case you’re not familiar with the show, George Michael Bluth is the teenage son of the main character, Michael. No relation to the singer/songwriter, though they have possibly been confused for one another down at the pier.
And George Michael Bluth certainly doesn’t apply to this conversation, he was in the first 10 seconds of the premiere. So I’ll shut up now.
Reverend Jim on Taxi. “Slow down”
Wesly and Fred on Angel, were some pretty good additions.
*Nitpick: those three were never cast members, so I don’t think they count as added characters.
Reminds me of when my brother-in-law watched “This Old House” primarily to laugh at Bob Vila. BiL is a hobbyist carpenter whose workshop now rivals Norm’s.
Scruffy on Futurama.
Bronson Pinchot’s Jean-Luc Rieupeyroux on “Step by Step.”
seven of nine
I think Slacker meant that George-Michael is giving Woody a run for his money as Slacker’s favorite character of all time.
Seconded.
Uncle Albert on Only Fools And Horses
(Do non-Brits know the show?)
I also wanted to say Winchester and Woody, but someone beat me to it.
I’ll bite…Whaaaaaaat dooooooeeeeees a yeeeellloooowwwww light meeeaaaan?
Slow. Down.
Practically the entire supporting “cast” of the Simpsons: while they only really provided background in the initial series, as they were developed as characters they shifted a lot of the immediate focus off the Simpsons themselves, and gave the principals any number of distinct characters to interact with - as the series developed further, the Simpsons often became peripheral to the antics of the “supporting” characters, with stalwarts such as Mr Burns and Krusty providing much of the comic meat, and relatively minor characters such as Troy McClure enjoying episodes of their own; this prevented {or delayed…} the antics of the Simpsons themselves becoming stale or repetitive.
On preview, that reads incredibly pompously: blame Askia; I’ve just come out of his"superheroes" thread, and I’m still in mock serious mode.
Don’t forget Poochie, and Roy. They are my favorite added characters on the Simpsons.

Don’t forget Poochie, and Roy. They are my favorite added characters on the Simpsons.
Heh. Meta-added characters.