Andy Cohen is obsessed with getting to the bottom of which “Dawson’s Creek” stars hooked up in real life. Just a couple of months after prodding Busy Phillips for behind-the-scenes dirt, on last night’s episode of “Watch What Happens Live,” Cohen was back at it again (in the form of a “viewer email”) — this time asking James Van Der Beek if he ever had a fling with Michelle Williams or Katie Holmes. After questioning whether he could “plead the fifth,” a blushing Van Der Beek coyly responded, “A bunch of young, twenty-year-old kids shooting in an isolated location filming love scenes with each other? Of course we never hooked up.” (Watch above.) Since that doesn’t exactly qualify as an answer, Andy better hurry up and book another “Creek-er” ASAP!!