An American in ParisGoofs
Just after the "Our Love is Here to Stay" dance Lise rushes off to met Henri at the stage door. Henri introduces her to an American producer who has invited him to perform in America. As soon as the producer leaves, Lise starts to apologize to Henri for being late. If you listen very closely, you'll notice that she starts speaking in French ("Je ....") She immediately catches herself and continues in English, "I'm sorry." Since both actors were Francophones, in real life they would naturally have conversed in French.
We see Adam in his studio three times. When we first see him, alone, he is playing a black baby grand. The second time, he is playing a brown baby grand upon which Jerry dances. In the third Adam studio sequence he is alone, again, playing the black grand. Perhaps the brown piano was fashioned to accommodate and withstand Jerry's dancing on it.
When Gene Kelly is painting Lise's portrait, she poses with a red carnation in her hand. When they lean in to embrace the carnation falls on the ground and is momentarily out of view. He bends to pick it up, but it's no longer a carnation but a red rose. The difference is quite obvious in the flower petal arrangements.