C## is a white key on the piano. Another name for C## is D, which has the same note pitch / sound, which means that the two note names are enharmonic to each other. It is called double-sharp because it is 2 half-tone (s) / semitone (s) up from the white note after which is is named - note C.
wild lines are lines that actors repeat when they weren't clear enough to be heard the first time. Theatrical productions are live, and you cannot go back and change what has already been done.
