Say good-bye to ER's Dr. Jing-Mei Chen. Again. In tonight's episode (10 pm/ET, NBC), Dr. Chen (aka "Deb") quits her emergency-room job and leaves in a huff. This is the third time Ming-Na's character has stormed off the show! "Once again, she's a quitter," the 41-year-old actress laughs to TV Guide Online. "She's just a spoiled brat who can't handle the pressure."

Ever since Chen's parents had that off-screen car wreck — her mother was killed — the lady doc's been burdened with caring for her widowed father, who's "mentally given up on living," Ming-Na says. After yet another personal conflict at work, she's outta there. The real reason she's exiting ER, however, is lack of a meaty story line.

"I think it was a mutual decision," Ming-Na says. "The producers definitely talked about running out of stuff to do with the character. I felt like it's been that way for the past year; I wondered if there's anything left. We both decided it's time to finish the character."

Aside from Chen's early friendship with Noah Wyle's Dr. John Carter, Ming-Na's fave plotline was Chen's emotional struggle with having an interracial baby, then giving the kid up for adoption. "I got to be pregnant on camera," recalls the Chinese thesp, who was carrying daughter Michaela, now 4, at the time. "We also addressed a very sensitive social issue people wouldn't want to touch, the conflict between blacks and Asians.

"What I also liked about Chen is, when she's in the ER, she's the total by-the-book professional who tries to do her job as perfectly as possible. But that masks who she is — a little wild thing. Remember when she got drunk and jumped off a stage into a little mosh pit?"

Ming-Na disapproved when Chen got too wild, though. "My least favorite thing was when they made Chen into the ER slut," she laughs. "She had an anonymous hook-up, and then there was [a semen stain] on her cashmere sweater. I hated, hated, hated that moment! All the women on the show hated that. What is this, Monica Lewinsky? We tried to fight it but [the producers] were like, 'It's funny'."

Post-ER, Ming-Na is excited to have the freedom (not to mention the healthy bank account) to take some career risks. "It's great," she says. "The world is my oyster." She's promoting an Asian-American boy band called At Last and developing her own sitcom concept to shop around to the TV networks. "I wanna do comedy!" she enthuses. "No more kids being thrown out the window, no more blood and gore."