* Scrubs (8 pm/ET ABC)
Scrubs wraps up its eighth season tonight as J.D. prepares to leave Sacred Heart and fantasizes about finally landing a hug from Dr. Cox and learning the Janitor's real name. But leaving the hospital isn't the only change in store for J.D. as Elliot slowly begins moving her things into his place, a clear sign that she's changing the course of their relationship. More than 50 past guest stars turn out for tonight's finale, a fitting tribute to this quirky and heartfelt show.
* American Idol (9 pm/ET Fox)
The final four singers are between a rock song and a hard place in tonight's results show. Last night, the remaining quartet - Kris Allen, Danny Gokey, Allison Iraheta and Adam Lambert - blasted through rock-and-roll tunes, putting some edge in the show while being mentored by Guns n' Roses and Velvet Revolver guitar master Slash. Sadly, one of our singers will be slashed from the contest before night's end. There's little doubt that rockers No Doubt will perform. And Daughtry, fronted by Season 5 contestant Chris Daughtry, are on hand to perform "No Surprise."
* Lost (9 pm/ET ABC)
Now we know exactly why the crash of Flight 815 happened. And we know about Faraday's theories for making it unhappen. What would happen then? We'll have a better idea next week, after "The Incident" happens to wrap up this season. But for now (1977, actually) Jack and Kate are at odds about what to do next, and the jig is up for Sawyer and Juliet at Dharma. And in 2007, Locke is fully in charge of the Others. What does that mean for Richard Alpert (not to mention Ben)?
* Lie to Me (8 pm/ET Fox)
Cal is going to jail tonight, but not for anything that he did: He's posing as a cop killer so he can get into the skull of a serial rapist (Rescue Me's Daniel Sunjata) whose MO - come on like a nice guy, then blind the victims before raping them - is being copycatted. This approach could yield clues for catching the copycat, but it won't be easy because the guy is both smart and a pathological liar. Mekhi Phifer guest stars as the skeptical FBI agent on the case.
Teyona strengthened her front-runner position with last week's double wins in the go-see competition and the photo shoot. Slight-of-height Fo wasn't so lucky and got the short end of the elimination stick, while golden oldie Celia narrowly escaped ouster (she bombed the beach photo shoot), due to her strong past pictures. But if she doesn't soon remove the "old-looking" label from her back, Celia is history. Fortunately, Tyra directs a jungle-themed photo shoot tonight that requires the final four models to resemble exotic birds. Maybe Celia can hide behind the distracting makeup and feathers.