PARIS — On one of the last days of Fashion Week here this past fall, the world’s most unusual store was bustling with desire. A young man was trying on a cartoonish but life-size leather snake, a handbag by the funky comedian of clothes Walter Van Beirendonck that wraps diagonally around the body. Two friends cooed over a fluffy pink double-breasted Dries Van Noten coat that looked like cotton candy tailored into stately submission. “It’s the only coat you’ll ever need,” one said, improbably.