For the first time in the history of the two long-running competitions, ABC's "Dancing With the Stars" outdrew both editions of Fox's "American Idol" last week. Meanwhile, the broadcast networks faced a ratings disaster on April Fools' Day that was no joke.

The Nielsen Co. said Tuesday that nearly 23 million people watched "Dancing" a week ago, while an estimated 21.8 million people watched "Idol" on Tuesday and 20.5 million on Wednesday. The ABC show has a strong cast, including reality-TV star Kate Gosselin, former "Baywatch" babe Pamela Anderson, astronaut Buzz Aldrin and Olympic gold-medal figure skater Evan Lysacek. Fox said "Idol" had a comfortable lead last week over its ABC rival among 18- to 49-year-old viewers, the audience Fox cares about almost to the exclusion of anything else.

Broadcast networks are also coming to grips with a "freaky Thursday" phenomenon that sent viewership plummeting on what is usually one of its most popular nights.

CBS' "CSI" and "The Mentalist" had the smallest audiences in their series' history last week, as did ABC's "Grey's Anatomy." Fox's "Bones" and CBS' "Survivor" had their smallest audiences of the season so far, Nielsen said.

The networks theorize the April Fools' doomsday could be explained by religious holidays for Christians and Jews, along with the onset of good weather on the East Coast.

1 Dancing With the Stars (ABC)

2 American Idol, Tue. (Fox)

3 American Idol, Wed. (Fox)

4 NCAA Basketball: West Virginia vs. Duke (CBS)

5 Dancing With the Stars, results (ABC)

6 The Mentalist (CBS)

7 NCAA Basketball, bridge (CBS)

8 Castle (ABC)

9 CSI: Crime Scene Investigation (CBS)

10 Undercover Boss (CBS)

11 Survivor: Heroes vs. Villains (CBS)

12 Two and a Half Men (CBS)

13 NCIS (CBS)

14 NCIS: Los Angeles (CBS)

15 Lost (ABC)

16 Cold Case (CBS)

17 Law & Order: SVU (NBC)

18 Grey's Anatomy (ABC)

19 The Big Bang Theory (CBS)

20 Modern Family (ABC)