Fox has a Thursday problem. The problem is X Factor followed by Glee. Their ratings are not catastrophic — they’re just not what the show once enjoyed, or what Fox would like to see again. The X Factor’s Thursday results show was down 25% in overall audience last season, and 21% in the demo (9.5 million viewers, 3.3 rating) compared to the season previous, and the season previous wasn’t anything to write home about — which is why all but one of the show’s non-Simon Cowell judges, and one of two hosts, are not returning in the fall. Glee, meanwhile fell another 13% in the demo, and 10% overall,  last season (3.3 rating,  8.1 million viewers) – and that’s with just one rerun in the ratings mix —  making it that show’s lowest-rated season yet.  Back in its second season, Glee managed to snag 10.3 million viewers and a 4.2 rating with around a dozen repeats factored in.

Enter Demi Lovato.

In one of those the-whole-is-bigger-than-the-sum-of-its-parts theme nights, the popular singer/former child star has been signed to appear in at least six episodes of Glee this coming season, while also appearing as X’s sole surviving non-Simon judge.  That’s at least six Lovato-themed Thursdays this season — more than a third of Glee‘s episode order for the season. It’s the former Disney Channel star’s first major acting gig since Sonny With A Chance called it a day. She’ll first appear in the second part of Glee’s Beatles tribute, on October 3, as TVLine noted.

Themed nights are nothing new to TV. Back in the 90’s, Elizabeth Taylor gave it a whirl, on CBS’ Monday sitcoms, with the thinnest of through-lines: she’d lost a black pearl necklace. In fact, in the 90’s, you couldn’t throw a dead cat without hitting a theme night on broadcast TV. They did well for networks, ratings-wise, and in UCLA Introduction to Communications classes professors taught students about NBC’s Hurricane Saturday, in which Florida-set Empty Nest, Golden Girls, and Nurses slogged though soggy storylines. The same network grabbed headlines when Seinfeld declined to participate in its NYC Blackout Thursday theme night. If Lovato Thursdays takes off, expect to see more of same across the TV firmament.