In the operating room scenes with Jack, Juliet's surgical cap moves up and down her forehead. During this time, her gloved hands are bloody, so if she had made an adjustment to her surgical cap manually, there would be blood visible on the cap like the blood that is visible on her surgical mask from when she pulled that down off her face.
During surgery, the audio pips of Ben's heart rate do not match his heart rate on the screen monitor.
The bus that runs over Juliet's ex-husband, supposedly in Miami, has the color scheme and unique rainbow decals found only on the public bus system in Honolulu where the show is filmed.
When Tom and Jack go to the observation platform to let Juliet speak privately to Ben, Tom says "I'm Tom, by the way." While the idea that Tom and Jack have gone through this crazy ordeal together without having ever been introduced, Jack learned Tom's name in the season 2 finale when Kate told Tom she knew he was wearing a fake beard and another member of the Others teased him for it. Tom even chastised her for revealing his name to Jack and his friends.
When Richard Alpert pitches his company to Juliet, each time he uses the remote control and the image changes, the digital video projector on the table makes the noise of an old slide projector advancing a slide.