I had a boyfriend who walked in his sleep too.
According to both him and his parents, one night when his parents had visitors he walked across the lounge stark naked and was about to urinate against the terrace door when his mother caught him by the arm and led him off to the bathroom. She then took him to bed. While she was trying to manoevre him into bed he grabbed her arm, pulled her down, leered at her and said, "We´ll have to be quiet, mum will kill me if she finds out I had a woman in here".