When Senator David Palmer and his chief of staff are in the limo discussing how to proceed in light of Ferragamo's death, the background in the rear window suddenly changes. When Palmer is saying "Maureen Kingsley is going to get the story of her career", trees and a vehicle suddenly appear where there was only blue sky.
When the chopper rescues Teri and Kim from the Gaines compound the CTU siege operative tells Teri to drop her gun, she promptly drops the gun, but a second later its back in her hand again.
The henchman that is looking for Jack's wife and daughter in the shack is called away to regroup by Gaines, and exits via some steps. After he has finished walking down the few steps, sound effects of footsteps descending steps can still be heard.
At 12:36pm when Jack, Kim and Teri are hiding behind foliage, Kim walks out, claiming there is no one around. At this point, you can clearly see the Effects Supervisor sitting on the grass, waiting for his cue to set off gun fire. He is wearing a beige jacket and a blue cap.
When Kim runs toward the tower to look for Rick you can see two crew members standing (then ducking) in the background.