By Tim Stack
March 31, 2009 at 12:00 PM EDT

No surprise, ABC’s Dancing With the Stars was far and away the Monday night winner with 20.2 million viewers, according to preliminary overnight ratings. The network’s mid-season series, Castle, meanwhile, held steady with 9.8 million fans, same as last week. Over on Fox, a guest appearance by rapper/actor Mos Def helped drive House to a solid 12.2 million. The night was not good for NBC’s Chuck, though, as the series struggled with only 5.6 million viewers.