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Charlotte and Cooper's new marriage certainly has been tested this season. First, he found out he has a son, Mason (Griffith Gluck) from a fling he had eight years ago with Erica (A.J. Langer), and juuuust when that reality had sunk in, they learned Erica has life-threatening illness that needs some highly specialized medical treatment.

If only they knew a (Mc)Dreamy brain surgeon! Oh right. They totally do.

In Thursday's Grey's Anatomy, Derek Shepherd's li'l sis Amelia (Caterina Scorsone) brings Erica to her big bro in Seattle to try to save her life, and Charlotte and Cooper come along for the ride to support Mason.

"We're looking for a miracle honey!" Kadee told me on the set of Grey's while filming, hinting to the mere seconds it may come down to to save Erica's life. "Yeah, it's a big deal. That's why we traveled. We can't leave our practice and our hospital for just anything!  We're here visiting the Dr. Shepherd family, and Chyler Leigh (Lexie Grey) which is great. We're having so much fun [on the Grey's Anatomy set]...It's kind of like a bizarre dream we're all living out."

Char-Coop fans have been dying to know if the couple might have a child of their own, and good news! Paul says he thinks it's becoming more and more of a possibility. "One of the fun things about it is that Charlotte is at best ambiguous about having kids," he explains. "And this [Mason] thing has been like thrusted into her lap. And Cooper of course has always wanted kids. So it almost works for them…It's really going to beg the question about whether they have their own because Charlotte has really taken to Mason now."

KaDee, for the record, is all for Char getting knocked up! "I would love to practice a waddle!" she laughs. "I just think that would be so fun. In my little cheap jacket, just walking around, be in a bad mood and having to puke, it would be good." You hearing this, Shonda Rhimes? Ratings. Gold. (Or maybe not but we would love it.)

So tomorow night, will Erica survive? Paul admits "We do know" but of course, they ain't spillin' cause they don't want their characters contracting a case of the "gonna die"'s, too. Kadee simply says she hopes Erica sticks around because she has a "mad crush" on actress A.J. Langer. Fair enough.

On that note…any chance Charlotte and Cooper will get back to some of their racier romance scenes? Where has the kink-tastic love gone? Get all the scoop from KaDee and Paul on that—plus why she was mortified to watch a recent episode of The Soup that made fun of her!—in our exclusive video interview from the Grey's Anatomy set.  Warning: It'll make you crush on them more.

The Grey's Anatomy-Private Practice crossover airs tomorrow night on ABC on both series. Don' t miss it!

More here:
Grey's Anatomy-Private Practice Crossover Scoop: Paul Adelstein & KaDee Strickland Talk Baby-Makin'!