Fast National ratings for Thursday, March 31, 2011.

ABC's "Grey's Anatomy" got a huge bump for its heavily hyped musical episode, but it was still FOX coming out ahead for the night with "American Idol" and encouraging returns for the special "Mobbed."
 
Among adults 18-49, FOX averaged a 5.2 rating for the night, topping ABC's 3.1 rating and CBS' 2.9 rating in the key demographic. NBC was fourth with a 1.1 rating, beating the 0.4 rating for The CW.
 
Overall, FOX averaged an estimated 16.43 million viewers and a 9.4 rating/15 share. CBS moved up to second with a 7.6/12 and nearly 12.1 million viewers, better than the 5.6/9 and 8.89 million viewers for ABC. NBC was a non-factor with a 1.5/2 and 2.375 million viewers, still better than the 0.8/1 and 1.18 million viewers.
 
8 p.m. - FOX's "American Idol" double-elimination episode drew 22.02 million viewers and a 6.7 rating among adults 18-49 -- both up significantly from last week -- to rule the 8 p.m. hour. CBS was second with new episodes of "The Big Bang Theory" (11.7 million viewers and a 3.6 demo rating) and "Rules of Engagement" (8.18 million and a 2.3 demo). ABC's "Wipeout" averaged 6.34 million viewers, beating the 2.21 million averaged by a repeat of "Community" and a new "Perfect Couples" on NBC. The CW's "Vampire Diaries" repeat was fifth with 1.2 million viewers.
 
9 p.m. - "Grey's Anatomy" moved ABC into first in the 9 p.m. hour with 12.72 million viewers and a 4.8 key demo rating, the show's best audience in months. CBS' "CSI: Crime Scene Investigation" averaged 12.485 million viewers for second. FOX's "Mobbed" special averaged 10.85 million viewers and a 3.8 demo rating for FOX. That's a big drop, but you can almost certainly expect to see more of the Howie Mandel series after "Mobbed" held all of its 3.8 demo rating in its second half-hour, an impressive feat for a post-"Idol" offering. NBC's repeats of "The Office" and "Parks and Recreation" averaged 2.77 million viewers, beating the 1.15 million viewers for The CW's "Nikita" repeat.
 
10 p.m. - CBS closed in first with the 13.86 million viewers and 2.8 demo rating for "The Mentalist." ABC's "Private Practice" rode the "Grey's Anatomy" bump to 7.6 million viewers and a 2.7 demo rating. That left NBC's repeats of "30 Rock" and "The Office" in third with 2.14 million viewers.
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.