In which film is Sandy Olsson a character?

In which film is Colonel Nathan Jessup a character? Who played Danny Zuko in 'Grease'? In which film is Danny Zuko a character? Who played Sandy Olsson in 'Grease'? Who played Tony Manero in 'Saturday Night Fever'? In which film is Tony Manero a character? Who played Johnny Castle in 'Dirty Dancing'? Who played Frances "Baby" Houseman in 'Dirty Dancing'?