Once & Again fans remember Marin Hinkle as Sela Ward's little sister, the jealous, moody Judy. Now, she costars as Judith, Jon Cryer's estranged — and possibly gay — wife on Two and a Half Men (Mondays at 9:30 pm/ET on CBS). But if you thought Hinkle played difficult drama queens in those roles, just wait till you see her on tonight's ER!

Basically, her part is every ER day player's dream: The freaked-out mother whose kid's undergoing a medical procedure in the emergency room. That kind of cameo just begs for an actress to run the scenery-chewing gamut, from fear to anger to full-on meltdown. Here's a little preview...

"My character is a mom who's driving with her husband and two kids and gets in a terrible car accident," Hinkle tells TV Guide Online. "I'm in shock, and it turns out that the driver who caused the accident is in the hospital right next to me!" Sounds like your typical wreck-of-the-week plotline, but she promises there is a twist, and it involves a heart ailment and a Hummer SUV. We'll say no more.

Happily for Hinkle, she didn't have to go far to do ER. The hospital drama and Two and a Half Men both shoot on the same Warner Bros. studio lot in Burbank, Calif. "When I auditioned," she says, "they asked if I minded switching from comic behavior to playing such tragedy in one day. But that's the joy of being an actor! It's fun to look made up and put together for a sitcom, then run over to ER and be a car accident victim, where you're mussed up and have blood poured all over you."