“Grey’s Anatomy” (9 p.m., ABC): It’s Halloween on “Grey’s

“Grey’s Anatomy” (9 p.m., ABC): It’s Halloween on “Grey’s Anatomy” and the day is full of surprises for the denizens of Seattle Grace. Alex receives an unexpected visit from his former patient Ava. Meanwhile, Meredith is convinced that her mother’s ashes are haunting her, and Callie spills the beans on George and Izzie’s affair.

“Scrubs” (9:30 p.m., NBC): Did they or didn’t they? When we last left the wacky docs of “Scrubs,” J.D. and Elliott — overwhelmed by the big changes in their lives — ended up in bed together. As the show launches what looks to be its final season, the two characters explore whether they have a future together.

“Iconoclasts” (10 p.m., Sundance Channel): Sean Penn meets writer-adventurer Jon Krakauer, and they walk the Stampede Trail, where backpacker Chris McCandless was found dead 15 years ago.