Other words that are associated with this are:
Doo Fairy (As in feces)
'Doo Fairy (As in Scooby Doo)
Do Fairy (As in doing things)
'Do Fairy (As in Hairdo)
Due Fairy (As in being due)
The nice thing about this insult is that it can be translated to any of the others without the person knowing, so an insult can be transferred into a compliment should your boss accidentally overhear you calling him a Doo Fairy or Dew Fairy. Simply switch to Do Fairy, and explain that you were simply saying he does a good job at doing his work, etc.
This insult is otherwise seen in the eyes of the beholder and can be translated however you'd like.