When the dance sequence with Gene Kelly and Jerry Mouse was screened for MGM executives, someone noticed that, although Gene Kelly's reflection shone on the floor during his dancing, Jerry's did not. This required animators William Hanna, Joseph Barbera, and their team to go back and draw Jerry's reflection on the floor as he was dancing.
One of the rare occasions when Jerry Mouse actually talks.
Although many have said that a longstanding resentment between the two leads was started during this project, there is little to no evidence to suggest this. Quite the contrary, it was this film that started a lasting friendship between Frank Sinatra and Gene Kelly that spawned two other film projects.
For the most famous sequence in the film, Mickey Mouse was originally meant to be the dance partner of Gene Kelly. However, when Walt Disney refused to have his most famous character appear in an MGM film, Kelly turned to MGM's own animation studio and used Jerry Mouse of "Tom and Jerry" fame. William Hanna and Joseph Barbera--the writer/directors of MGM's "Tom and Jerry" cartoons--supervised the animation for the sequence. The scene initially didn't work: in Jerry's dances with Kelly, the animators had forgotten to add shadows for Jerry. Additional moneys had to be allocated to cover the 10,000 new drawings that would be required.