The good news is that Fox has finally established the elusive Thursday beachfront with American Idol. The bad news is that it came with a price, sending the reality hit to its lowest-rated second night premiere ever. Surprisingly, the casualties were limited for the Thursday 8 PM shows under assault; not surprisingly the other reality show in the hour, ABC’s Winter Wipeout, was impacted the most. And somewhat surprisingly, NBC’s three-hour comedy block did better than expected.

In its Thursday debut last night, Idol drew a 7.8 rating among adults 18-49 and 22.9 million viewers from 8-9 PM. Vs. the show’s second night premiere on Wednesday last year, which was 90 minutes, the show was down 20% in 18-49 and 13% in total viewers. In the more apples-to-apples comparison of this year’s Thursday opener to the 8-9 PM hour of last year’s Wednesday premiere, the declines were 15% in 18-49 and 9% in viewers. At 9 PM, Bones (3.6/9) hit a season high but held onto a so-so 46% of its Idol lead-in (It’s always been hard for scripted shows to follow Idol; Fox has had better success with unscripted fare behind the reality juggernaut.) What’s more, Bones faced weaker than normal competition in its first outing at 9 PM as the time slot leader, Grey’s Anatomy, was a repeat. With Idol and Bones, Fox easily dominated the night and logged its highest-rated Thursday night with regular programming in 15 years, since Feb. 3, 1995.

NBC’s all-comedy Friday lineup was off to a promising start, especially the network’s 4 established series. Community (2.2) had an impressive showing, posting its second best demo rating this season behind its highly rated signature Halloween episode. Vs. its most recent original on Dec. 9, the show was up 16%. In its first regular airing, new comedy Perfect Couples (2.1) retained an OK 95% of its lead-in. (However, 30 Rock regularly built on its Community lead-in in the slot.) Perfect Couples also proved once again that comedies do much better when they are in a block with other comedies as it was up 62% from its preview behind the Sing-off finale in December. The Office, boosted by a lot of publicity surrounding Steve Carell’s departure, the show’s search for his character’s replacement as well as Ricky Gervais’ upcoming appearance, shot up to a 4.5 demo rating, up 22% from the show’s last original on Dec. 9 for a season high. In its return after a seven-month hiatus, Parks & Recreation (3.2/8) hit a series high, up 52% from its fall season premiere in 2009 and retaining 71% of its Office lead-in. (Its predecessor in the slot, freshman Outsourced, averaged a 65-70% retention.) At 10 PM, 30 Rock (2.7/7) was up 29% from its last original at 8:30 PM, but a pretty solid night for NBC ended  with a bit of a downer as Outsourced (1.8/5) at 10:30 PM was down 28% from its last original telecast behind The Office. So, judging by the results last night, the answer to the question whether 10 PM is too late for comedies should be: No, but 10:30 PM may be, especially if your comedy is not that strong. Still, the bar has been pretty low this season – both 30 Rock and Outsourced outperformed The Apprentice to post NBC’s best numbers in the 10 PM hour this season.

It seems like with the addition of Idol, the Thursday primetime universe has expanded (the geniuses from The Big Bang Theory should know all about that) because the hit CBS comedy was left mostly unscathed last night. Big Bang (4.2/12) was down 5% in 18-49 and 3% in viewers. $#*! My Dad Says (2.7/7) at 8:30 PM also held up well, down 7% in the demo. The rest of CBS’ lineup was also down, CSI (3.1/8) by 6% and The Mentalist (2.8/8) by 10%.

As expected for a reality show going against a bigger reality show, ABC’s Winter Wipeout (2.6/7) took a hit, down 28% from last week but still did solid business for ABC in the hour. The network aired repeats for the rest of the night.