You've got to hear Kim Kardashian's explanation for why she doesn't smile

Kim Kardashian is known for a certain look: her "serious" face.

Some might say she looks fashionable, and some might say she just looks sad all the time.

But she does smile -- just not that often. She even laughs "on occassion." So why do we not see this more, you ask?

"Because it causes wrinkles," the reality-TV star explains on Twitter.

Err, we're not quite sure whether she's joking or not...

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