Once CBS moved Survivor off of Thursdays, Fox knew it had to make a move. That’s how the net execs explain their decision to change the American Idol lineup from Tuesdays and Wednesdays to Wednesdays and Thursdays in January. “We’ve been thinking about this move years because Thursdays are so lucrative and so important to the network and the sales division,” explains Mike Darnell, Fox’s head of reality programming. “As a network, we’ve never been able to conquer that night. We’ve tried in some way for 20 years but we’ve never had anything big there. Once they moved Survivor out of 8, which was the last surviving reality show in that timeslot, that got [head of scheduling] Preston Beckman thinking that now is the time to do it. Other than The Big Bang Theory, there really is not much on. “

He’s got a point there. Big Bang has continually won its timeslot in adults 18-49 and viewers (14.84 million) this season but it’s lead-out, $#*! My Dad Says, hasn’t exactly held onto every last one of those Theory fans (11.54 million). Still, CBS’ new comedy that stars William Shatner has been able to dominate at 8:30 p.m. because it airs opposite a repeat of Grey’s Anatomy and 30 Rock, which has never been able to muster a big following.

“That timeslot looks ripe, it’s the right moment,” explains Darnell, who also goes onto explain why Fox abandoned the idea of airing a 30-minute results show. “If you are going to attack Thursdays, you need to attack it with your biggest piece because that’s the only way anyone has ever won on that night. And if you are going to make this move, you have to have an hour show. You can’t go in with a half hour. The new format and the things happening with the show are going to make that hour make much more sense.”

And what about those new changes? Even though exec producer Nigel Lythgoe has been out there discussing a change to the top 24 and having contestants do music videos, Darnell insists that nothing has been set in stone for the new season. “First of all, while are going to be making changes to the middle round, we wouldn’t go with no top 24. That has not been decided. We’ve talked about a lot of things and yes those middle rounds are going to be different, but it’s not like there is not going to be a top number of contestants for the audience to vote down to a top 12.”

As for Fox’s other big newsmaking move – shifting Fringe to Fridays – Entertainment President Kevin Reilly said he hopes fans don’t think he’s putting the show out to pasture. “We are not killing the show. Over the last week, over 45 percent of the audience time-shifted the show. That’s almost half of the dedicated audience watching it on their DVRs. It’s been such a loyal fanbase. I will be really disheartened if the viewer base decides to not watch because it shifted one night. I hope they go with it, and if not they have the option of picking it up on their DVRs. If it does anywhere near what it did on Thursdays, we can glue that show to the schedule because it can be a big win for us.”