Natalie Portman in Thor

I see that Natalie Portman is to star in the love interest in Kenneth Branagh's movie of the Marvel Comic Thor.

Which is an excellent reason for this old joke...

Thor comes down to earth and shacks up with a woman. After a week he tells her "I must return to Valhalla, I'm Thor".
"You're Thor?" she asks "I'm so Thor I can't pith".