While I'm certain that Sunny's personality would be instantly grating in real life, on the screen it really makes for some good scenes. Over-the-top forced cheerfullness and exhibitionism are quite when you know for certain that you never have to deal with this person with her clothes on.
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[The movie business] is a cruel and shallow money trench, a long plastic hallway where thieves and pimps run free, and good men die like dogs. There is also a negative side. - Hunter S. Thompson