Her performance may have gone down well with critics and audiences, but acting alongside Britney Spears was apparently a disconcerting experience for her How I Met Your Mother co-stars.

The reason? The proper actors on the set of the quirky US comedy were reportedly put off their craft because the singer declined to take off her sunglasses until the cameras started rolling.
 
A show insider tells the National Enquirer: “Britney delivered her lines, but the show's actors had a tough time reading her expressions since they couldn't see her eyes at all.
 
“It's hard for an actor to make a connection when all he sees is his own reflection staring back at him in shiny dark glasses, but no one wanted to upset Britney by asking her to take them off.

“In the end, someone said to her, ‘You will be taking the sunglasses off for the actual tapings, right?’ To which Britney responded, ‘Uh...yeah!’ ”

Shady behaviour aside, Brit’s comedic turn proved a massive hit with audiences, giving the show its highest ratings ever.

It emerged yesterday that Brit is set to auction off the outfits she wore during the episode, in which she plays a receptionist who develops a crush on a patient played by Josh Radnor.

Click here to check out the sexy receptionist threads up for grabs.