You aided Jacobo and Ned in the creation of the monsters, and were distraught when Mystery Inc. destroyed them, so you brought some of them back yourself after Jacobo and Ned got arrested.

Currently, you're sitting in the front drivers seat of your van with the Black Knight Ghost in the passenger, and The Pterodactyl Ghost is sitting in the back with the one-eyed Skeleton Twins, Red and Green, with the 10,000 Volt Ghost, and it's a bit of a tight fit for the four back there, but they agreed to a roadtrip, so they have to deal with it.