The little spanky moment featured Eric Dane and Kate Walsh, pictured below. (The Kate Walsh photo is by Tim White)
I'm not going to go into the details of the plot. It's really not that important. All you really need to know is that Eric (Dr. Mark Sloan) and Kate (Dr. Addison Montgomery) wind up in her office at the clinic, door closed, blinds pulled, with the two of them getting naked and going at it first on the sofa and then spilling over onto the floor. This is Network TV, of course, so it's all shot very discreetly.
The scene in question starts with them side by side on the floor, hot and sweaty in the afterglow. Addison rolls toward him, going in for another kiss, but can't help making a little remark about his ex-girlfriend.
There's a quick change in camera angle and we're left looking at the top of the furniture--a chair close to the camera, and the sofa across the room. The two are obviously on the floor in-between. From the bottom of the screen we see Sloan's arm come up, and then quickly come down, followed by a sound effect of a very satisfying "whack!"
The camera cuts back to a head-and-shoulders shot of the two of them, Addison's eyes and mouth wide open in astonishment as Sloan admonishes her to not make fun of his ex. Addison says, "Did you just spank me?" She's laughing by the end of the question, and trying to crawl on top of him.
He tries to grab her hands and replies, "Yeah. You looking for trouble?" to which Addison responds, "Maybe" and it turns into a little bit of a wrestling match between the two of them, during the course of which we hear--but again, do not see-- another slap and a yelp from Addison.
Of course, before this could possibly go any further, the door opens and they're interrupted by another doctor at the clinic. Sloan and Addison are left scrambling to cover themselves up.
For a little scene where everything is heard and nothing actually shown, it was well done and quite fun.
Addison's line was an echo from the film, "Along Come Polly" starring Jennifer Aniston and Ben Stiller. Ben is told by a friend that women like a little spanking, so while he and Jennifer are making out, he reaches back and gives her bottom a little smack. And Jennifer (the Polly of the title) says, "Did you just spank me?" The difference, of course, is that in the movie we get to see it--or, at the very least, we got to see Ben Stiller's hand-double give a little swat to Jennifer Aniston's butt-double. You can never be sure with the way Hollywood films things. But the expression on Kate Walsh's face really sells the unseen swat, and makes this scene just as good.
And, of course, this post wouldn't be complete without one final paparazzi photo of Kate Walsh on a windy day for those wondering just what Dr. Sloan was spanking: