In the scene where Forrest is talking about how he got his name, It goes to footage of the KKK. When the leader goes back toward the group and turns around to go the other direction, you can see tire marks appear in the lower left of the screen. This is from when they recorded the Tom Hanks footage, there was no tire marks like there was in the original footage. When put together, they didn't bother to cover up the tracks from the original footage.