It’s insidious. Pure evil. Those teeny-tiny almost subliminal little hashtags that have been popping up on FOX shows? Have you noticed? They’re everywhere all of a sudden. I first noticed them on Glee last night. As Finn and Rachel danced at the prom, under their heads popped #finchel – Fox’s gentle suggestion that I ought to start tweeting about them ASAP. Telling me what THEY think should start trending. “We’ve noticed shows like Glee and Idol trend while the show is on, but fans often use different hashtags,” Fox marketing president Joe Earley told TV Guide. “We thought if we provided the official hashtags, then more posts would aggregate.”

So far, only a handful of shows are using them (Fringe, Glee, Bones, and Breaking In). Twitter, of course, loves it and has been encouraging broadcasters to include them, citing several examples on its media blog along with the corresponding tweet spikes. “Think about it this way: as a viewer, the bug reminds you what network you’re watching; the hashtag reminds you that there’s a conversation happening,” says Twitter’s Robin Sloan. Implying: YOU COULD BE A PART OF IT! DON’T BE LEFT OUT!

So it’s a marketing tool for Twitter and the network. But I think we’ll be seeing a lot more hashtags on TV in the months to come. And where does it stop? Will advertisers start adding hashtags when their products are being used in a scene? And will your whole screen eventually be cluttered with an glut of overlapping twitter suggestions? YOU HAVE BEEN WARNED!

Of course as Bluegrass points out: “Online communities for TV shows have been around for a long time (X-Files forums, anyone?). Having real-time conversations via social networks is simply another way for fans to deepen engagement with one another. The least TV networks can hope for by using TV hashtags is a more dedicated fan base that tunes in each week and also creates online buzz through live discussions.” What do you think? Have you noticed them yet? Does it make you want to start tweeting?