The Simpsons characters mentioned here started out nameless. Their nicknames were originally created by fans of the show. The names became so frequently used on the Internet that the writers eventually worked some of them them into the show itself (just like they worked in order elements of Simpsons fandom such as "worst episode ever" declarations). Comic Book Guy and Bumblebee Man have been called that on-screen as a reference to the show's cult following. Others such as Squeaky Voiced Teen, I believe, are still unattested in the show.
Actually, hasn't Teen Titans
given away Starfire's name when the visited her planet a few seasons ago?
Yep, but they didn't explicitly say it; you had to listen for it when her surrogate dad starts yelling at her when they arrive.
I don't remember the exact episode, but there's an episode of Homicide: Life on the Street where one character mentions that he can't recall the name of some doctor, with the reason being that the writers hadn't given him one.
: Removed the Buffy example, as "Spike" was retconned into a deliberately-chosen nickname, and he had other names ("William the Bloody") people knew him as. Aside from the deliberately-chosen angle, "Angel" actually would have a better case for belonging, since even in flashback to his living days they avoided mentioning his real name (and only ever revealed his given name). I don't think adopted names and codenames are really the same thing as this trope, though.
: Such a short trope description doesn't merit a second quote, so put here instead:
You've been sacked, Colonel. Colonel:
ROAR! You can't strip me of my rank, because then I wouldn't have a name. KILL. Lackey:
OK, fine, but was the gutshot necessary? Ow.
--Toastyfrog Thumbnail Theatre: Akira
Removing from the page:
Revealing, to this troper's dismay, that it's actually pronounced Tēdus instead of Tīdus.
Fear not! Word of God
has said that the KH pronunciation was simply Wakka's island accent (or some such nonsense). He is, in fact, called Tīdus.
Now, that's simply untrue. In multiple interviews and other promotional material, James Arnold Taylor (his voice actor)and other members of the FFX cast & crew also pronounce it Tee-dus. And as a hopelessly devout fan of both FF and KH, I can assure you that no such Word of God
For the record, he's called Tīdus in Kingdom Hearts 2
by Selphie. --Heroic Jay
Would Shadow from American Gods count? The original book goes to odd, alhtough subtle, lengths, to avoid mentioning his name; it's only mentioned in passing in the sequelette, "The Monarch of the Glen".