I always thought Kristen Wiig looked like Jennifer Aniston. Jesse Plemons is a Mat Damon lookalike (when not too heavy). Also been re-watching Roswell and the guy who plays Michael (Brendan Fehr) totally looks like what a young John de Lancie would look like! Also, more than a passing resemblance, Krysten Ritter and Audrey Hepburn.
I don't see a similarity between Wiig and Aniston at all, but you're on the nose about Plemons. When I saw him in "Black Mass", I thought it was Damon with makeup appliances! I didn't realize it wasn't Damon until I watched the end credits! (In my semi-defense, the fact "Mass" took place in Boston added to the confusion since Damon has such ties to that area...)
Speaking of Roswell (in my previous post), Maria (Majandra Delfino) looked like a ringer for Molly Ringwald, especially with her S1 haircuts. You don't think she doesn't look like Aniston, at all?
I always thought that Jason Bateman and Jerry O'Connell looked alike when they were younger and both wore their hair similarly. (Some people also think a younger Nathan Fillion, from Firefly, looks like them also, but I don't see that as much as I do with the similarities between Bateman and O'Connell.) Liev Schreiber resembles them a little bit too.