Paul Adelstein on Private Practice Twist: Cooper's 'Best Case Scenario' Threatens Charlotte

Private Practice‘s Cooper got a blast from the past – especially considering it’s one he never knew existed! — when a onetime hookup showed up at his workplace with an 8-year-old in tow. This Thursday (on ABC, 10/9c), he has the delicate task of getting to know young Mason while managing Charlotte’s reaction to the arrival of the child her husband always wanted, and at the same time tempering his own paternal feelings.

“The thing that Cooper’s having trouble with, and it doesn’t do him any favors, is he feels like this is like the best case scenario for him, to a certain degree,” Paul Adelstein tells TVLine. “He’s not convinced that this is actually his kid yet, but I think he’s kind of hoping that it is, especially after this one cute scene where he tries to get to know Mason. He’s just totally smitten.”

So piqued is Cooper by the prospect of insta-fatherhood, his joy bubbles through even when it should not – meaning, when he updates his wife on the sticky situation.

“When he presents it to Charlotte, he tries to be sensitive but it’s hard for him to hide his excitement,” Adelstein says.

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Cooper’s immediate bond with Mason raises flags for his friends and coworkers, who urge him to keep things in check until the boy’s paternity can be confirmed. “By their estimation, Cooper is being naïve,” Adelstein says. “They think he should be a lot more cautious before he gets too invested in this kid. But he’s willing to just kind of jump with both feet.”

One looming question is: Why now? Why did this Erica (played by My So-Called Life‘s A.J. Langer) after so many years decide to clue in Cooper? “Nobody knows, and that’s why people are kind of advising caution,” Adelstein answers. “Her upfront justification is this kid has been asking about his father, and she thought it was time for him to meet him. But other people assume other things are going on there.”

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What Adelstein likes about this take on the age-old paternity bombshell storyline is the fact that Erica is not some “great first love” of Coop’s, or even a former steady. “He has no investment in this woman at all, and she doesn’t have any investment in him other than this potential offspring, and that makes the child relationship primary. And what’s especially powerful about it is this is a guy, a pediatrician, who’s always wanted children, and he’s in love with a woman who’s lukewarm on the subject. So basically he’s presented with this opportunity, whether it’s a fraudulent one or not, that’s very enticing to him.”

If Mason does prove to be Cooper’s kid, will it effectively table the always-prickly family planning discussions between him and Charlotte? Or might it actually amplify that hot topic in some regard?

“It shines a light on it, very brightly,” Adelstein previews. “Charlotte has this really romantic line — Cooper says, ‘You don’t even know if you want children,’ and she says, ‘Well, I might have thought differently about that had I known somebody had already done that for you.’ So, yeah, she does feel threatened for his affection — not by Erica, but by Mason. That’s a relationship she could potentially get cut out of.”