Last week, it was reported that the beautiful Kaley Cuoco of The Big Bang Theory was taking on a role as a guest star on the Grey's Anatomy Season 5 finale May 14.

However, just as soon as Cuoco's guest role was announced, she suddenly rescinded the chance to appear on the medical drama. Why the strange, abrupt bailing?

EW reports that the actress' rep claims a "publicity commitment" forced the star to back out of a top-secret appearance on Grey's Anatomy. But multiple sources say it was her Big Bang employer, CBS, that nixed the deal - clandestinely or otherwise.

CBS couldn't be reached for comment, but an insider explains, "They didn't want one of their biggest stars appearing on one of ABC's biggest shows." Makes sense.

As a result, Grey's Anatomy has instead tapped former OC starlet Shannon Lucio to fill Cuoco's shoes. Still unknown is who the character will be exactly.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.