Comment by the_af

> Keira Knightley & Natalie Portman

Wait, which one is the "off-brand" here?

> Bryce Dallas Howard & Jessica Chastain

I must confess I used to confuse these two!

Another one you didn't mention: until relatively recently, I thought actors Elias Koteas (Exotica) and Christopher Meloni (CSI: Special Victims Unit) were the same person!