A smile on Kristen Stewart's face is like a real body part anywhere on Heidi Montag's body.

Both these examples are as rare as Sarah Palin turning down a speaking engagement.

But the Twilight Saga star says she isn't actually miserable on the red carpet, "it’s just that somebody’s yelling at me... I literally, sometimes, have to keep myself from crying... It’s a physical reaction to the energy that’s thrown at you.”

That's an unusual way of putting it, and an unfortunate circumstance for someone often forced to attend movie premieres.

In the latest issue of Elle, Stewart opens up about a number of other topics, as well, including (of course) Robert Pattinson:

On responses to her public mannerisms: “I think it’s funny that when I go onstage to accept an award, they think I’m nervous, uncomfortable, and awkward - and I am - but those are bad words for them.”

On problems with fame: "I can’t be by myself and I like being by myself.”

On being in a relationship: "I would never cheapen my relationships by talking about them. People say, ‘Just say who you’re dating. Then people will stop being so ravenous about it.’ It’s like, No they won’t! They’ll ask for specifics."