Some rumors are so ridiculous, it's amazing that celebrities even respond to them. But apparently Kristen Bell just couldn't let the latest one go.

The pregnant actress has slammed a veterinary technician for claiming she and boyfriend Dax Shepard had sex at an animal hospital while their pet Shakey was being examined.

Star magazine published a story claiming the couple made love at the Laurel Pet Hospital in West Hollywood, Calif. A source explained: "Another employee walked in on them, and they was basically on the exam table. Kristen apologized and explained her pregnancy hormones just made Dax irresistible - even in the vet's office."

How kinky - if it was true.

Bell responded to the rumors on Facebook, posting: "Haha this is gross. Obvi (obviously) this never happened and if I ever WAS turned on around the smell of dog p**s I certainly wouldn't apologize for it...Thanks to whichever dude at the Laurel Pet hospital had the integrity to make up and sell a story. You are a real piece of s**t. See you never again!"

The couple's first child is due to arrive this spring, and they plan to wed after same-sex unions are legal in California. Bell has admitted she's nervous about giving birth, telling Ellen DeGeneres: "I feel like, when I arrive at the hospital, I want a glass of whiskey, I want the epidural in my back and I want to get hit in the face with a baseball bat and wake me up when it's over because I've seen the videos - and it looks terrifying."