On the DVD, Taina Elg says the original cast was supposed to include Cyd Charisse as the American girl, Leslie Caron as the French girl and Kay Kendall as the English girl. Cyd Charisse decided to do Silk Stockings instead, so Mitzi Gaynor took her part. At one point, Kay Kendall didn't want to do the film and Taina Elg was tested for her part. Ms. Kendall took the part after all, but then Leslie Caron withdrew. Tania Elg was tested for THAT part and received her first major film role.
The last musical and movie Gene Kelly made for MGM under his contract. It wasn't until the documentary That's Entertainment, Part II that he would appear in another MGM musical.
This was last movie Cole Porter worked on.