Okay, train of thought here: by the end of this season Supernatural will be the longest running US genre show. Prior to Smallville, Stargate: SG-1 held that title. (Huh--just noticed they're all "S" titles, and short.) On SG-1, there are characters who die a bunch of times and come back to life--just like Sam and Dean, except Sam and Dean do it without alien technology, and also the general public knows that Sam and Dean have "died" a bunch of times. If they were on Highlander, the Watchers would totally think they're immortals. Has anyone written that story? Because it wouldn't take a whole lot to make those worlds mesh: Highlander already has demons in it (although they're a little different than SPN's), and the immortals could totally be descended from Nephilim or something, with their "quickening" actually being a destorted form of grace. Or something.
I'm not writing this (like, seriously--not writing this, so don't even suggest it), but it would be interesting to see what someone else could do with it.
Of course, the question is, would they be able to keep everyone in character? Because that's always the issue with crossovers, especially when both sets of characters are uber-capable in their own canons. (I shake my head over all the Teen Wolf-Supernatural crossovers where Sam and Dean suddenly can't cope with a bunch of teenaged werewolves. I mean, seriously? They've been doing that sort of thing since before they were teenagers, they've taken out demons, angels, even gods, and somehow a bunch of brand-new werewolves are too much for them? Makes me laugh in disbelief.)
Anyhow, just something that crossed my mind, and I remembered that I used to stick this kind of stuff up here, so I figured, why not?