The Funny Games actress admitted that Schreiber's "big head" means that they are often recognised by fans when in public.
"I don't have strong features. I'm small and I just kind of blend in with the rest of the world," she told the Daily Star.
"Liev is big, he has a big head, and is very much himself. There's really no-one that looks like him."
Watts was recently announced as the face of Ann Taylor's fall fashion line.