"Kyle XL" (8 p.m., ABC Family). Season finale. So will otherworldly Kyle (Matt Dallas), the quizzical boy with no belly button, finally get some answers to his mysterious origins? Well, a couple of folks claiming to be Kyle’s mother and father do show up at the hospital to take him home after last week’s mishap at the carnival. Hey, not so fast, Mom and Pop. There must be a paranormal cliffhanger to keep us guessing.

Now this is TV...

"Prison Break" (8 p.m., WJBK-TV, Channel 2, Fox). What’s up, Doc? Leave it to T-Bag (Robert Knepper) to find a crazy, sinister solution to his medical crisis. A stressed-out veterinarian gives him a hand. Meanwhile, sibling fugitives from justice Michael (Wentworth Miller) and Lincoln (Dominic Purcell) take a sudden detour to try to rescue Lincoln’s son, only to come face-to-face with FBI Agent Mahone (William Fichtner), their obsessed new nemesis. It’s one of the killer thriller’s best episodes.

Prom blight

"How I Met Your Mother" (8:30 p.m., WWJ-TV, Channel 62, CBS). Boppin’ at the high school hop. When Lily’s (Alyson Hannigan) wedding date is pushed up, she grabs Barney (Neil Patrick Harris) and Robin (Cobie Smulders) to crash a high school senior prom so they can check out a potential band for the wedding. But the prom just reminds Lily of all the post-graduations that were derailed by her relationship with Marshall (Jason Segel). Oops, sounds like a case of impending pre-marital doubt and discord. (Rerun)

What number is Paris?

"101 Guiltiest Guilty Pleasures" (9 p.m., E!). Quick, shut off your brain. Mindless eye candy escape arrives as E! revs up the pop culture trash machine and spits out a four-night countdown of extreme guilty pleasures. Yep, pet clothes, boy bands, televised police chases, Paris Hilton, makeover shows, Riverdance and many, many more are here for your lowest-common-denominator entertainment.

Is her face red!

"The Closer" (9 p.m., TNT). Everybody plays the fool sometime. Now it’s Brenda Leigh Johnson’s (Kyra Sedgwick) turn in the embarrassing spotlight. She can say hello to workplace mortification now that her past romantic relationship with Police Chief Will Pope (J.K. Simmons) is about to be revealed to the whole detective squad by Pope’s angry, estranged wife. Have a nice day, Brenda.

Among the ’Weeds’

"Weeds" (10 p.m., Showtime). Love is strange. And so suburban pot dealer mommy Nancy Botwin (Mary Louise Parker) and her DEA agent main squeeze, Peter (Martin Donovan), must now try to work out the rather odd kink in their relationship. Meanwhile, Shane (Alexander Gould) has a close encounter with puberty. And while Nancy’s away, Uncle Andy (Justin Kirk) becomes an unlikely fount of practical birds-and-bees wisdom.

Back to New Orleans

"Nightline" (11:35 p.m., WXYZ-TV, Channel 7, ABC). Terry Moran is down in New Orleans to anchor the first report in "Nightline’s" two-night commemoration of the first anniversary of Hurricane Katrina and the historic storm’s tragic devastation.