What's Worth Watching: American Idol, Big Bang Theory, Grey's Anatomy and more for Thursday, May 7.

Matt Roush
American Idol, Dalton Rapattoni
Michael Becker/ FOX

American Idol (8/7c, Fox): Over so soon? Fox may have rushed this final season of its former pop phenom to what seems a too-early conclusion, but they're not skimping when it comes to gathering past Idols and fan favorites—including the notorious Sanjaya!—for the grand finale. Headliners include Carrie Underwood and Kelly Clarkson, with Jennifer Hudson and Phillip Phillips late additions to a lineup that includes a winners' circle of Ruben Studdard, Fantasia, Taylor Hicks, David Cook, Kris Allen, Lee DeWyze, Scotty McCreery, Candice Glover, Caleb Johnson and Nick Fradiani, plus a nostalgia tour featuring the linkes of Ace Young, Blake Lewis, Bo Bice (now with Blood, Sweat & Tears), Constantine Maroulis, Chris Daughtry, Katharine McPhee, Kellie Pickler, LaToya London, Melinda Doolittle, Tamyra Gray, Lauren Alaina and plenty more. The official end time is 10:06/9:06c, at which point a new Idol is expected to be named. Will it be the diva (La'Porsha) or the soulful farm boy (Trent)? With this much star power, will we even notice?

The Big Bang Theory (8/7c, CBS): Used to be American Idol was such a powerhouse that no one would put significant programming up against the finale (which tender to air the last night of the traditional TV season in May). Sign of the times, as TV's top comedy airs a new episode, in which Sheldon (Jim Parsons) blurts a secret about Leonard (Johnny Galecki) when they take their honeys on a weekend cabin trip. On producer Chuck Lorre's other hit comedy, Mom (9/8c), Christy (Anna Faris) becomes personal assistant to the demanding Jill (Jaime Pressly), a gig we have to assume is temporary. And William Fichtner begins a recurring role as a new man in Bonnie's (Allison Janney) tumultuous life.

Grey's Anatomy (8/7c, ABC): The Shondaland lineup is all new as well, led off by the enduringly popular Grey's, during which Meredith (Ellen Pompeo) learns what's really behind the estrangement of Owen (Kevin McKidd) and Nathan (Martin Henderson) as they ride together in an ambulance. Back at the hospital, Wilmer Valderrama (That ’70s Show) guests as a musician with MS.

Inside Thursday TV: Animal Planet's most popular series, River Monsters, returns for a new season (9/8c) that sends Jeremy Wade out of his comfort zone into the deeper depths of ocean waters. First subject: "Deep Sea Demon," as in sea serpents. … On ABC's The Catch, the new client played by Alan Ruck is the estranged husband of Valerie (Rose Rollins), but Ruck is actually married to series star Mireille Enos. … Fresh off his Wisconsin primary win, with sights set on New York, where a Democratic debate will be staged next Thursday, Bernie Sanders visits NBC's Late Night With Seth Meyers (12:35/11:35c).