New photos and video released Tuesday reveal a more subdued look appropriate for the mousy, lovesick receptionist she plays in the episode.
In a promo for the show, a bespectacled Spears is shown with her hair pulled back into a simple ponytail, and wearing a demure cardigan.
In another scene, she appears a little sexier dressed in a red silk blouse with her hair down and the glasses gone.
"Can we have sex and then go shopping?" she asks Barney (Neil Patrick Harris), the show's incorrigible playboy.
In the promo, Spears sits behind the receptionist desk at the medical office where she's working for a doctor (Sarah Chalke) who's being pursued by the show's main character Ted (Jason Radnor).
The episode featuring Spears airs on CBS Monday, March 24, 2008.