Earlier today, ET confirmed that BRITNEY SPEARS was signed to make a guest appearance on CBS' "How I Met Your Mother." Now, ET's KEVIN FRAZIER gets the 411 from series star NEIL PATRICK HARRIS on the role the pop princess will play.

"I was shocked that Madame Spears was willing to come and do some acting," Neil tells Kevin. "She hasn't acted in a while. This is a very interesting role. It is very not like her at all in real life in any of her previous chapters. She plays the secretary to another girl that Ted [JOSH RADNOR] is after. So, it will be very unlike any Britney we have seen before, and we have seen a lot of Britney recently."

Neil also says that the cast and crew of "Mother" are not gearing up for an onslaught by the paparazzi, because they do not film on location, but rather on the FOX lot.

He does kid around, however, floating a theory that the pop princess may secretly be a tabloid headline mastermind!"

"What if she shows up on set and she is absolutely, totally normal and that whole thing has been a big ruse?" he jokes. "She is smoking a cigarette and [says], 'Oh yes, it is all a big bit. I have a master plan.'"