The GM me is in theory a very control and detail obsessed maniac who in practice is overly lax and allows a lot more than he claims he will.  For instance in one of the RPs I had that was successful (for a RP, anyways) I explicitly banned aliens that weren't alien alien.

Than proceeded to allow human-like aliens early on as a 'exception' to the rule because I figured it might happen at least once.

Than other humanoids appeared anyways.  But I accepted them because digitrade legs, no visible mouth, grey skin color and vertical blinking eyes sounded alien enough.

Than the *shudder* space furries started appearing and I start freaking out.

All the while I was crystalline machines that lived off of blood somehow when not being sacs of flesh (with hand mouths) that get churned by industrial machines.

The GM also has a bad habit of being like a man on a island alone jumping around hoping someone notices him.