Corrected entry: At the end of the film, Lina (dubbed by Kathy) announces that she will sing "Singin' in the Rain" in A flat. Moments later, the song begins in E flat.
Corrected entry: Near the end of the movie, when Debbie Reynolds is supposed to be dubbing Jean Hagen's singing and dialog for "The Dancing Cavalier," Debbie was actually lip-synching to Jean's real singing and dialog. In other words, the dubber was dubbed by the dubbee.
Correction: This is a common Hollywood urban legend. Though both Debbie Reynolds and Jean Hagen were exceptional singers, Betty Noyes sang "Would You?" and "You Are My Lucky Star."
Corrected entry: During the Good Morning song when Cathy is sitting on the steps watching Cosmo dance the hat she has on disappears.
Correction: The hat doesn't disappear, it is on the steps beside Kathy, most of it is obscured by the raincoat but you can still see quite a bit.
Corrected entry: When Don Lockwood jumps into Kathy's car to get away from his fans, from the above shot you see her look upwards just after he drops. In the very next shot, Don is on top of the seat and Kathy is looking straight ahead, then turns to look at him, surprised.
Correction: I checked frame by frame, she's wearing a hat, and it never moves on the long shot. She is looking straight ahead the whole time.
Correction: Actually, the song is still in A flat. She only starts singing on an E flat. There is still the D flat in the key signature. In fact, the note on the 'in' in 'Singin' is a D flat.