In another episode, Summer Glau made an appearance. They mentioned the Sarah Conner Chronicles more than once. I don't think they mentioned Firefly at all, but then that is the show for which she is best known in the nerd community and that is not the audience to which BBT is geared..
To be fair, I believe the Terminator show was currently airing when that episode first aired. No doubt Glau wanted to promote her current show more than the one that had already been cancelled . . . which makes sense.
Plus, here's the thing: despite what some fans might think BBT should
be, the show is a network sitcom aimed at general audiences and is not intended to be enjoyed by nerds only. So, yeah, all other things being equal, it's only smart to go with "nerdy" references that the whole audience will recognize rather than deliberately go with something more obscure than only hardcore geeks will appreciate. What's the point of making a FARSCAPE joke that nobody but nerds will get when a STAR WARS joke will work just as well?
It's all about when tailoring your material to your audience. When I'm speaking at a Trek convention I can refer casually to "Journey to Babel" and "Amok Time" and assume that the audience will get the references. But if I'm speaking at a public library or elementary school, I'm going to assume a less specialized knowledge base--and talk more about Superman than, say, The 4400
. . . .
And, no, that's not "dumbing it down." It's about communicating effectively with your audience--and not trying to be deliberately obscure just for the sake of showing off your nerd cred.
You don't get points for leaving ninety percent of your audience in the dark . . .