Chris Pratt was making $1.5 million for the entire movie. The set was burning $20,000 a minute. And the director's choreography notes for the climactic scene of a $170 million film were two words: "Just dance."He was a sitcom supporting actor. Parks and Rec had originally cast him as a guest star. He'd never led a film. And now he was standing in front of 200 extras in full alien prosthetics, with 20-foot flames behind him, improvising a dance sequence that would either define or destroy the cha