I've had a bumpy ride on this one and now is time to ask for help from my friends. I finished the grid remarkably quickly (by my standards), although I cannot parse 13 across for the life of me. I know the 4x4 which is the last three letters backed, but where do the other two come from?
I guessed the film from the title, assuming it is the most famous quote, confirmed by the first word of the misprints, I know the shape but where does the 29 cell start? Are all 26 letters (Bar one?) in the extra words?
Or, to put it another way, we are well into the week so someone please help!!