I too am a lover of the movie. Not long after it came out, I watced an interview with Shelley Duvall and she talked about her audition for Olive Oyl.

She said it was the shoes.As soon as she put them on she went straight into Olive.She hadn't rehearsed the part and had no idea what she was going to do.Once the shoes were on she went with the flow and got the part.

Great movie.

rr