Who's this trenchcoat-wearing shady lady?
Remember, you must be a registered user of TheInsider.com to participate. Take a look through the photographic evidence and leave your best guess in the comments section below. Tune in to "The Insider" on TV and your name may be the one called out on the air -- but only if you guess the mystery star!
Here's a hint: This pop star once voiced Charlie Brown's kid-sister, Sally, on two of the Peanuts' animated TV specials.
Watch our video to find out who correctly guessed Tuesday's mystery star!








After Britney's performance, which pop star would you like to see make a guest appearance on "How I Met Your Mother"?
Jessica Simpson
Madonna
Mariah Carey
Beyonce
Lindsay Lohan
Tina, St. Joseph, MI.