Doug, a dorky young mamma's boy, who is about to get married to his beautiful bride, Callista, when he notices a change come over her. He catches her sneaking around at night and lying to him, and she's begun to display flu-like symptoms. So naturally Doug thinks she caught a disease while cheating on him. In reality she has become possessed via an ancient stone and she's been eating his friends and family without him knowing. When the truth comes out Doug and his remaining groomsmen (his best friend, his robot, and a Luchador) must team up with a psychotic gardener to stop Callista and her demon-possessed bridesmaids before they kill everyone in sight.

School is out and the familiar Scooby gang are looking to enjoy a long vacation. However, sightings of a Lake Monster cause them to band together once again to solve yet another mystery.