Isla Fischer / Amy Adams
Margot Robbie / Samara Weaving / Jamie Pressley
Justin Long / Ezra Miller
Not to mention all of the token/stereotype characters where it hardly matters who the actor is at all. Need to fill the funny fat lady trope? If Rebel Wilson wasn't available, maybe they can get Melissa McCarthy.
The voice from Her isn't even the first voice I'd think of for a female computer voice. That trope has been around for decades. I'm sure OpenAI just wanted SJ specifically because she's currently one of the most popular celebrities in the world.
Bryce Dallas Howard & Jessica Chastain
Selena Gomez & Lucy Hale
Amy Adams & Isla Fisher
Keira Knightley & Natalie Portman
Not to mention that anytime an actor ages out of the early adulthood age range, a lookalike begins to play the same roles.
If you can't think of any examples, it's probably because you haven't been able to tell them apart yourself.
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!