I always felt the John Burns character never quite fit the rest of the ensemble of 'Taxi' I just found out from an article that John was written off the show because the writers felt the same way. What was really interesting however, is when the same writers created 'Cheers' & after Nicholas Colasanto died, they created the "Woody Boyd" character which was based on John Burns....

John Burns (played by Randall Carver) was intended in Taxi’s first season to represent the small-town boy overwhelmed by the big city.