Audio problem: When Turk comes in to tell everyone that Dr. Kelso has ruptured his eardrums, Dr. Cox starts to say, "Bob you stupid mother..." from the back view. Then it cuts to a different camera angle, and he is mouthing the words, "stupid mother" again.
Audio problem: When Bri-Bri says this hospital is hot his mouth moves before the words come out. (00:08:30)
My Best Friend's Wedding - S3-E22
Audio problem: If you look at the band's mouthes in the back round, they are completely out of sync with the song for a verse. (00:19:05)
Answer: No, it was a fake, they used a stamp.
It is real.