Have any questions about sperm banks?

Don't bother asking Jennifer Aniston.  

On Thursday's The Tonight Show With Jay Leno, the 41-year-old actress promoted her latest comedy The Switch (out Aug. 20), in which she plays a single woman seeking a sperm donor.

When Leno asked her how sperm banks work, Aniston got flustered.

"You go to a bank and you have a card..." she stammered (see video, above). "I honestly don't know exactly."