Random Doodles has a set of characters going in and out. This page lists most of them, though not all of them have appeared (yet) so keep an eye out!
(More detailed descriptions to follow).
The Occult Police
Hmmm. I’m eagerly waiting for Mabel and the Occult Police to show up. at least, I don’t think they have yet?
The Occult Police should be soon! But Mabel will be awhile yet; she’s a pretty late addition to the cast.