Fast National ratings for Thursday, April 23, 2015.

Even though Thursday night was just April 23, it represented the start of the still-important May Sweeps period. As rumors of a show-changing twist spread, "Grey's Anatomy" got an impressive 33 percent key demo bump over last week and helped ABC split the night with "Big Bang Theory"-driven CBS.

"Grey's Anatomy" was actually the only thing that was up on Thursday night, as decliners included all of CBS' originals, "The Blacklist," "Scandal" and "American Crime."

Let's get to the numbers...

Among adults 18-49, ABC and CBS both averaged a 2.0 rating for Thursday night, tops in the key demographic. There was a huge drop to NBC and FOX's 0.9 key demo rating and to The CW's 0.5 key demo rating for Thursday.

Overall, CBS was in control with an estimated 9.405 million viewers and a 5.9 rating/10 share for Thursday primetime. ABC's 7.115 million viewers and 5.0/9 finished second, well ahead of the 5.48 million viewers and 3.6/6 for NBC. FOX's 3.78 million viewers and 2.4/4 easily beat The CW's 0.8/1 and 1.12 million viewers for the night.

8 p.m. - CBS started primetime in first overall, but second in the key demo with "The Big Bang Theory" (14.4 million and a 3.5 key demo) and "The Odd Couple" (9.47 million and a 2.0 key demo rating). ABC's "Grey's Anatomy" had its biggest numbers since the season premiere with 9.43 million viewers and an hour-winning 2.8 rating among adults 18-49. FOX's "Bones" averaged 4.56 million viewers and a 1.0 key demo rating for a distant third. A repeat of "The Blacklist" averaged 3.44 million viewers and a 0.5 key demo rating for NBC, compared to the 1.39 million viewers and 0.6 key demo rating for The CW's "The Vampire Diaries."

9 p.m. - CBS remained in first overall and second in the key demo for the 9 p.m. hour with a new "Mom" (9.04 million and a 1.9 key demo) and a "Big Bang Theory" repeat (8.26 million and a 1.7 key demo). ABC's "Scandal" was second overall with 7.77 million viewers and won the hour with a 2.3 rating among adults 18-49. NBC's "The Blacklist" was close behind with 7.23 million viewers and a 1.4 key demo rating. FOX's "Backstrom" averaged 3 million viewers and a 0.8 key demo rating in fourth. The CW's "Reign" pulled in a weak 841,000 viewers and a 0.3 key demo rating.

10 p.m. - "Elementary" closed CBS' overall sweep with 7.63 million viewers in the 10 p.m. hour and also led with a 1.3 rating among adults 18-49. NBC's "Dateline" averaged 5.77 million viewers to beat the 4.14 million for ABC's "American Crime," while both networks averaged a 0.9 key demo rating.

All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.

A long-time member of the TCA Board and a longer-time blogger of "American Idol," Dan Fienberg writes about TV, except for when he writes about movies or sometimes writes about the Red Sox. But never music. He would sound stupid talking about music.