This van has several origins, in the episode It's Mean, It's Green, It's the Mystery Machine, we learn that the former owners of the van were a popular family whose children formed the musical group known as Mystery Kids. We also learn that it is this family that is the origin of the decoration of the van (colors, flowers and name). Another story of his origin is offered in the movie Scooby-Doo! The Mystery Begins. The van would be the vehicle of the gardener who worked for Daphne's parents, the latter had to have this car for her 16th birthday, towards the end of the film the gang paints and decorates the truck which becomes the Mystery Machine. So which is your favorite version?