NOT is one of the least personable of the Functions. It is likely, however, that this is simply because most of the other Functions deal with the denizens of the Puzzlebox more often, while it deals with maintaining the overall "physical laws" of the place.
Its nickname is "Spanner" and it can be sometimes heard by the sound its personasuit takes and by the Announcements the Puzzle gives. It has been involved in saving the Puzzle more than once.