Wow, old thread.
A couple not already covered:
Emma Stone and Jane Levy:
Sorry, not even close. Aside from both having dyed red hair -- both are natural blondes. Jane's thinner and shorter, Emma has a huskier voice, and Emma's face is wider/rounder. On top of that, I think Emma is stabler considering that she didn't get married and divorced in her early-20s.
Sometimes, Amanda Peet looks like she has a lot of Courtney Cox in her:
MotionMan
I used to confuse Dax Shepard with the guy that did "Scrubs"
I'd always thought that it was Toby McGuire in October Sky. For like 10 years.
Also, that movie where they play brothers. It's fucked up, man.
"They" who?
MotionMan
Alicia Witt and Judy Greer
Thomas Jane (Punisher, Hung) and Christopher Lambert (Highlander). Those two are really close.
http://www.imdb.com/name/nm0000483/
http://www.imdb.com/name/nm0005048/
I can never keep them straight (I was just watching Deep Blue Sea and it made me think of this thread).
MotionMan
Also:
http://www.imdb.com/name/nm0001173/
MotionMan