There are many little things in the movie Grease that make me wonder what was choreographed, what was accidental, what was just left in to avoid doing a re-take, or what was left up to the performers to improvize?
For example, at 3:00 of this clip of Beauty School Dropout, Stockard Channing as Rizzo stops singing, looks to her left, then resumes singing.
At 1:32 of this clip of Summer Nights Frenchy is handed a juice box that she doesn't do anything of significance with for the rest of the song.
In this movie how much of these little details are choreographed? How much is accidental? Or, if that is too broad: what about these two specific examples?