It has to be one of the Triumverate of Tools or Undie. The only other one I could think of that no one has mentioned would be Undie's butthole buddy termite.
You know what just occured to me?
Principle has denied being Skinner AND Will but has NEVER denied being Termite...or made any comments whatsoever about.
In fact at one point he was rather annoyed sounding with Skinner...