Just tell them the truth (maybe with a bit of diplomacy).
"Sorry guys, but we would really prefer it if Rocky stays home this time. He's great, but the last time he was here, he gave me a migraine, terrorized our cats, and tracked dirt all over the upstairs carpet. I hope you can understand..."
If they still get all butt-hurt, tell them:
"Fine bring the little fucher, then for New Years, we'll come over to your place with the Rottweiler and Bull Mastiff I've had my eye on at the pound. Sound like a deal?"
