Rooney explains to Conan what a merkin is: "It's like a wig for your ladybits."
CONAN: Now, in the books, the girl with the dragon tattoo based on the books by Steven Larsen and your character is a redhead, Elizabeth.
And you guys didn't go that way in the movie.
ROONEY MARA: No.
She's a redhead but dies her hair black.
Was very important to me.
Because I was a follower of the books.
CONAN: You wanted to be true to the books.
ROONEY MARA: Yes.
But obviously there's no way to really depict that in a movie.
Except I had to wear merken.
Do you know what a merken is?
CONAN: Andy knows what a merken is.
ANDY: Oh I know what a merken is.
CONAN: I do know what a merken is, a wig for down below.
ROONEY MARA: A wig for your lady bits.
CONAN: This interview's over.
so you wore one of those for that movie?
ROONEY MARA: Yeah.
They didn't ask me to but I'm naked so much.
And I wanted one.
It felt like a little fur bikini.
but I had to --
CONAN: Like what's your perv now.
Tell me more about the fur bikini!
ROONEY MARA: It was really cute.
And I had them make it Strawberry blonde.
Now, is that something that you -- that you give that back when you're done or do you --
ROONEY MARA: No, I have it.
CONAN: You have it.
You want to keep that.
A lot of creeps on E-Bay.
ROONEY MARA: I know.
You're very -- oh, shut up!
Leave me alone.
They always pick on me.