Something for the weekend: the mystery of Cyd's skirt

Here's a mystery: Cyd Charisse is clearly wearing a skirt with a pleat at the start of this lovely number with Fred in the 1957 SILK STOCKINGS. But if you look closely during the number it turns into a pair of culottes, presumably to aid the high kicks - but did they think nobody would notice? Maybe they didn't. Cleverly edited though ...

It becomes fairly obvious during the "Fated to be Mated" duet between Fred Astaire and Cyd Charisse that Charisse is wearing a skirt one moment and culottes (or flared shorts) the next. The bottom half of her costume changes on each cut of the dance when they are doing deep knee bends, and this is where the culottes show. For the upright spins and lifts, the skirt shows. The dance was obviously performed twice and edited into one sequence.