Grey's Anatomy Grey's Anatomy

Meredith is bright and shiny, Callie has kids with Owen, and Derek and Addison are still married.

These are just a few of the ways the world of Grey's Anatomy is turned upside down when Meredith imagines what life would be like if her mom had never gotten sick. In a special alternate-reality episode, airing Thursday at 9/8c on ABC, Ellis Grey (Kate Burton) was never stricken with Alzheimer's, and Meredith (Ellen Pompeo) had a very different upbringing. Instead of dark and twisty, Meredith is happy and engaged... to Alex Karev (Justin Chambers)!

Bad news MerDer fans: Derek (Patrick Dempsey) and Addison (Kate Walsh) are also still married. And she's pregnant!

Check out photos from Grey's Anatomy's alt-reality episode hit the set of Grey's Anatomy to get the scoop on the new Seattle Grace gang. Plus: Check out a first look at the alt-reality episode!

Meredith is pretty in pink: "She wears a lot of pink, and she's in love with Alex Karev," Pompeo explains of this very different, very happy Meredith. "They're like the perfect, preppy, yuppie couple. She's also still always trying to please her mother and she's vying for her approval all the time." 

GREY'S ANATOMY's Alt-Reality: Ellis Grey lives!

Grey's Anatomy's alt-reality episode |Grey's Anatomy|

Derek is grumpy smurf: Without Mer in his life, Derek is still unhappily married to Addison, which has greatly affected his personality. "We call him McDreary," Pompeo says. "He's a grumpy guy in the hospital, nobody likes him and nobody talks to him."

Addison is still around: Since Mer never got in between Derek and Addison's failing marriage, Addison never left Seattle. Instead, "she's majorly in denial," Walsh says. "She's a little different, not as bitchy, but still bitchy. It's a nice surprise for the 'Addek' fans, to see one take of what they would've been like if they were together. It's not necessarily so pretty."

Ellis is large and in charge: Since Ellis was never diagnosed with early-onset Alzheimer's, she was able to stay at Seattle Grace and move up in the ranks. "She's such a huge name in the medical profession," Chandra Wilson explains. "She runs that hospital with an iron fist, so you have to be at the top of your game when you're dealing with her."

Richard is with Ellis: In this reality, Richard Webber (James Pickens Jr.) finally got up the nerve to leave his wife Adele to be with Ellis. "We see a Richard who is very much in love with Ellis," Pickens says, "but he's also concerned that she has alienated her daughter. We finally see him take a stand and tell Ellis that she's subverting this girl's ambitions. Ellis understands it, but she also knows how to work Richard as well and she has a way of manipulating the situation and getting him to align with her."

GREY'S ANATOMY's Alt-Reality: Callie is married to… Owen?

Grey's Anatomy's alt-reality episode |Grey's Anatomy|

Miranda is "Mandy": As we saw in the flashback episode in Season 6, Bailey used to be a shy intern who went by the nickname Mandy. "We're revisiting Mandy," Wilson says. "She kind of got stunted right there at Mandy since the Chief wasn't able to mentor her the way we know that he had. She's just as smart, just as competent, but hasn't gotten to the place where we know Bailey will just go off on you in a minute. She had to keep it in check with Ellis Grey being in charge."

Owen is married to Callie: "Callie (Sara Ramirez) being with Owen (Kevin McKidd) is the largest mistake of both of their lives," executive producer Shonda Rhimes says. "It's very funny because they so have no business being together. She's so pining for this peds surgeon and she doesn't know why. It's because she never had Mark Sloan (Eric Dane) there and Erica Hahn (Brooke Smith) never came because Callie was the heart surgeon. She never had her first experience with a woman." (To note: Kim Raver's Teddy is still in Iraq, though she and Owen keep in touch.)

Callie is head of Cardio: "This Callie is a cardio surgeon," Ramirez explains. "She's close with Ellis Grey, who heavily mentored Callie. The result of Ellis Grey having mentored Callie really influenced the direction she took so Callie is really at the top of her game in this reality."

Cristina is flying solo: Without Meredith as her person, Cristina (Sandra Oh) has become a very stern, lonely, serious doctor. "For me, my inspiration was Emily the Strange and Wednesday Adams," Oh says of playing the new Cris.

GREY'S ANATOMY's Alt-Reality: Dorky Alex!

Grey's Anatomy's alt-reality episode |Grey's Anatomy|

Arizona is ... still looking good to Callie: "Arizona is much more sophisticated and polished. Everything about her is ambiguous; she's not with anyone, male or female," says Jessica Capshaw. But even in the alt-reality world, Calzona is meant to be. "You start to see Callie questioning what would have happened had she made a different decision, and that is inspired by a certain pediatric surgeon," Ramirez adds. 

Bonus Scoop: Pompeo and Chambers, who might just be the only Seattle Grace characters who haven't hooked up, will be smooching. "Oh my god," Pompeo says of her reaction to reading the script. "You have to understand, Justin is like my brother. I was so not into kissing him. I love him, and I think he's one of the hottest guys on the planet for the record, but yeah, it's like kissing your brother."

Are you excited for the alt-reality episode? Watch the first 10 minutes of the episode here — where you'll find out just what happened to Lexie (Chyler Leigh) — and then hit the comments with your thoughts. Check out another sneak peek below:

GREY'S ANATOMY's Alt-Reality: Addison is back!

Grey's Anatomy's alt-reality episode |Grey's Anatomy|