According to
this interview with IDW editor Denton Tipton, IDW pitched the BBC on three crossovers last summer at SDCC, and it was
Star Trek that the BBC gravitated to, partly because of the reaction IDW got from
Trek fandom over the announcement of
Star Trek/
Legion of Super-Heroes at the con.
I'd speculate that of the other two crossovers IDW pitched, one was probably
Doctor Who/
Transformers.
Doctor Who/
G.I. Joe doesn't really click in the mind, so that probably wasn't the third.
Doctor Who/
True Blood could be fantastic, but it would be a pairing of
Doctor Who with a mature property, and the BBC would have probably nixed it on those grounds. Same too with
Doctor Who/
30 Days of Night (which, personally, I think would be fantastic). So I think we can rule both of those out.
We can also rule out
Doctor Who/
Angel, which would have been awesome, but the
Angel license was done at IDW by last summer.
Doctor Who/
The Rocketeer would be a
ton of fun, but that wasn't likely to have been the third, either. Same with
Doctor Who/
Godzilla.
I'm leaning toward
Doctor Who/
Locke & Key or
Doctor Who/
John Byrne's Next Men as the third crossover concept IDW pitched to the BBC, but they're both kinda niche properties in comparison to
Doctor Who.
Now, if there's a crossover
after this upcoming
Star Trek series, I would
love Doctor Who/
Mars Attacks.
