bells and whistles

bells and whistles n.  [by analogy with the toyboxes on theater
   organs] Features added to a program or system to make it more
   {flavorful} from a hacker's point of view, without necessarily
   adding to its utility for its primary function.  Distinguished from
   {chrome}, which is intended to attract users.  "Now that we've
   got the basic program working, let's go back and add some bells and
   whistles."  No one seems to know what distinguishes a bell from a
   whistle.