* Scrubs (8 pm/ET ABC)
It's a battle of the exes tonight as Elizabeth Banks and Scott Foley return to Scrubs, reprising their roles as J.D. and Elliot's former flames. As J.D. tries to simplify his life for the sake of his son, he decides it's time to make peace with Kim. But he's not prepared to discover that Kim has a new man in her life: Elliot's ex, Sean. Awkward. Meanwhile, Turk turns to his friends at Sacred Heart to help him land a big promotion.
London won't be calling on designers in Brazil. Her recent weight gain cost her a trip to Sao Paulo, where the six remaining models travel to tonight. A scavenger hunt around the city awaits them, and the search tests the gals' navigation skills. The ladies pose as cultural icons for the photo shoot before the judges send one girl back to the U.S. Steady Teyona, who won best photo last week, now looks to be the front-runner.
* iCarly (8 pm/ET Nickelodeon)
A green-themed episode fittingly airs on Earth Day and finds Carly, Sam and Freddie getting a school assignment that requires them to create a project that will benefit the environment. Carly works hard at the task, but she accidentally builds something illegal: a nuclear-powered generator. Oops.
Ratings don't lie, and that's certainly good news to crime-fighting psychologist Cal Lightman (Tim Roth), who'll wind up this series' encouraging first season over the next few weeks with time-honored guest-star intensity. First up: L Word alum Jennifer Beals, beginning a story arc as Cal's ex-wife, an assistant U.S. attorney who's stumped on an arson case. Cal, as it happens, isn't entirely over her. In fact, he acts downright dumb around her. But does he act dumb enough to blow the case?
* Reno 911! (10:30 pm/ET Comedy Central)
If you've ever detected a flair for the dramatic in Jim Dangle, you won't be surprised to learn that he's rented out the Sierra Historical Society to stage a murder-mystery dinner, which is the focus of a two-part episode. (Part 2 airs next week.) What is a bit startling, however, is his decision to invite his ex-wife, her ex-fiance and her new fiance, so one may wonder if the menu includes a recipe for disaster. Rachael Harris and Scott Thompson guest star.