Has to be Doctor Who. It would work so well for both franchises: Another weird alien character with amazing abilities for TOS, another future human space exposition for Who.
Jean Airey's The Doctor and the Enterprise fic (infamously published without her permission with a cover to make it seem like a parody although it isn't) is pretty much exactly how I imagine it, although I think you could mix any Doctor with any Trek and it'd work just as well.
The Wounded Sky. And yes, one of the Enterprise crew was converting old 2-D entertainment video in to holo-video. And, it was clearly meant to be Tom Baker as the Doctor, so yes in the Trek universe (or at least Diane Duane's interpretation thereof), Doctor Who is an old fictional program.
Yes, reading
The Wounded Sky (1983) gave me the impression that
Doctor Who, like a work of fiction should be, was fictional in the universe of
Star Trek. But
Doctor Who seems to be real in Barbara Hambly's novel
Ishmael (1985)
:
The British TV series
Doctor Who is referenced at least four times: the
Fourth Doctor is described on page 13, Metebelis crystals from the serials
The Green Death and
Planet of the Spiders are mentioned on page 57, the
Second Doctor is described on page 154, and Kirk recalls legends of
a planet of
stagnant time-travellers in the Kasteroborous galaxy on page 200.
https://en.wikipedia.org/wiki/Ishmael_(Star_Trek)
So any fictional universe that includes both those
Star Trek novels would seem to have
Doctor Who both fictional and real somehow. And I'm sure some fans consider all the different
Star Trek novels to be in the same fictional universe. As I remember, the James Dixon chronology attempted to put all the
Star Trek productions, comic books, comic strips, short stories, and novels into one all inclusive chronology, So in the James Dixon chronology both
The Wounded Sky (1983) and
Ishmael (1985) are part of the
Star Trek universe and thus
Doctor Who is somehow both fictional and real in James Dixon's version of the
Star Trek universe.
And there is precedent for something to somehow be both real and fictional in a work of fiction.
TV Tropes discusses shows that in the Nick Verse or Schneiderverse and mentions such situations several times:
Continuity Snarl: The concrete canon nature that iCarly, Victorious, Drake & Josh and
Zoey 101 exist in the same reality with each other, then having the cast of
Victorious say that
Drake & Josh was a tv show. This came the episode after they had Helen, a major character on
Drake & Josh show up on
Victorious and reference Crazy Steve.
Celebrity Paradox: Several actors have shown up as themselves on various shows in the
Nick Verse despite playing characters that exist as real in the same universe. The most obvious example would be Drake Bell showing up on
Zoey 101 as himself, despite his character Drake Parker existing as a real person in the same universe that
Zoey 101 and all the other
Nick Verse shows are part of.
Recursive Reality/
Recursive Canon/
Mutually Fictional: Probably averted (probably because of how complex these tropes are). Even though
Drake & Josh exists in the same universe as the rest of the shows (as can be seen above) the
Victorious episode
Who Did It To Trina has the characters come out and say that
Drake & Josh was a TV Show. Despite this, neither of these tropes probably (again, complex) apply.
https://tvtropes.org/pmwiki/pmwiki.php/Series/NickVerse
https://tvtropes.org/pmwiki/pmwiki.php/Main/MutuallyFictional is described as:
In Show A, you watch TV. In show B, the TV watches YOU. This is a special kind of crossover trope in which the characters from Show A will enter the universe of Show B—both shows of which are "real" to us. In other words, neither is a
Show Within a Show. In addition to finding out that they're trapped in the universe of Show B, the characters of Show A discover that they themselves are the subject of a Show A in the universe of Show B. The characters from Show A are, in essence,
simultaneously Trapped in TV Land and a
Refugee from TV Land. This isn't
Real World Episode, since both universes are depicted as being
equally "real".
Arrgh! This is so common it's actually a trope!
Therefore it is conceivable that
Doctor Who might somehow paradoxically be both fictional and real in the fictional universe of
Star Trek. I don't understand how it could be possible for something to actually be both fictional and real at the some time, but it is obviously possible to write a story A in which story B is both fictional and real, since it has been done. The concept makes me feel like a computer that Kirk is about to short circuit, but obviously there is nothing to stop writers from writing the worlds that will make something both fictional and real in a story..
And there is a thread about whether
Star Trek is in the MCU.
https://www.trekbbs.com/threads/star-trek-is-part-of-mcu.293148/
And there in posts # 6, 11, 13, 15, 40, 41, 42, 49, & 51, I mentioned many other works of fiction that some sources claim are part of the same fictional universes as
Star Trek, so any future crossovers between those stories, novels, television shows, movies, etc., and
Star Trek would not necessarily be creating new links between them and
Star Trek but might be merely reinforcing preexisting links.
And there is another thread about crossovers between various television shows:
https://www.trekbbs.com/threads/ridiculous-crossovers-youd-like-to-see.268483/page-21#post-12913966
