You don’t have to be a brain surgeon to following all the comings, goings, crossovers, new jobs and new deliveries happening both on and off screen at Grey's Anatomy.

But it would help.

Fortunately, Grey's Anatomy cast members Chandra Wilson and Sara Ramirez chatted with TV Guide and offered up a special diagnosis for this week's episode and beyond.

First up, Wilson’s Dr. Miranda Bailey will be headed to Los Angeles for sun and apparently some fun when she crosses over to Private Practice, ABC's sister show, this week.

“I’m being overprotective of a patient I have that of course their care has to happen in L.A. at St. Ambrose – because that’s the only place it can be in the world,” she said.

“So I’m heading over to Private Practice!”

Grey's Anatomy leading ladies Chandra Wilson, left, and Sara Ramirez.

“You know, Taye Diggs’ character is single now!” Sara Ramirez reminded her co-star, nodding to a recently teased smooch between Bailey and Diggs' Dr. Sam Bennett.

But Wilson won't bite. “I don’t share stories,” she insisted, chuckling.

Despite Bailey’s interlude in SoCal, the rest of Seattle Grace is about to feel a chill as the result of the merger with Mercy West, which will put some docs' jobs in jeopardy.

“Not everyone at Seattle Grace is safe,” hinted Sara Ramirez, and Wilson took it even further: “Next week is a jaw-dropper. It’s not going to work out for some people.”

Wilson will also be stepping behind the camera as the director of the seventh episode of Grey’s Anatomy's sixth season, airing toward the end of October (the plotline is apparently Patrick Dempsey-centric – “all Derek all the time,” she teases).

Ramirez says Wilson’s directorial style is far from iron-fisted.

“She was amazing and we all fell in love with her as a director,” Ramirez said. “There was just a calm, grounded energy about Chandra when she walks in, and everybody just kind of feels it. And it’s so nice and you don’t feel rushed and you don’t feel crazy."

"But the reality is that in this industry there is always a clock going, there’s a budget, there are all these things ... but this woman is so grounded and so comforting.”

Wilson countered that her "calmness" may have been due to her acting skills.

“After the fact I can say I was as nervous as I-don’t-know-what,” she said. “But I knew that everything works from the head out so whatever it was that I put out there, I felt that’s what was gonna come back, and a lot of times I felt like we were like ‘Let’s get together and do a SHOW!’

As for Ramirez’s character, she says “Callie has the job of an attending, which is really exciting because her father – they’re on the outs, Callie and her father."

"That was sort of her financial support as well, and Callie’s dad comes back with an unexpected guest to deal with the falling out and the relationship with Callie and Arizona.”

Also coming back is Ellen Pompeo, post maternity leave. Thanks to advance planning and a quick birth bounce-back by Pompeo, Meredith will be in every episode this year.

“We shot ahead and she left, and now she’s on her way back,” said Wilson.

In fact, the Seattle Grace set may start looking more like a maternity ward when the cameras aren’t rolling: Pompeo and Chyler Leigh recently had babies, Katherine Heigl and her husband just adopted and Eric Dane's wife is rumored to be expecting.

Ramirez confessed that “I haven’t been drinking the water," but that "people are just settling down. And good for them, you know? Children are a beautiful thing.”

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.