When John Gage is organizing receipts and paperwork on a table at the fire station, a few envelopes and scraps of paper fall to the floor and remain at his feet. He then packs the materials from the tabletop into an envelope and tosses them into a trash can several feet away. In the next shot, the papers on the floor are no longer there despite having never been picked up (or noticed) by Gage.
Obvious square outline of new sod around the abandoned well.
At the overturned car crash, the Station 51 crew employs the Jaws of Life to extricate Freddie (the male victim); during this, his legs move. Once Johnny gets to him, Freddie says he "can't move" and "can't feel anything". While it is possible usage of the Jaws of Life caused minor leg movement, one of his legs moved upward several inches.
When the boys reach the abandoned well the woman trapped inside has clearly sunk up to her waist in the dirt. However, when the guys get her out of the well her slacks are completely free of dirt.
While the leads are talking in the hospital hall foreground, an extra dressed as an orderly is mopping the floor behind them. However, he is putting little effort, not paying attention to what he's supposed to be cleaning, and keeps pretend-mopping the same area over and over again, turning to face the camera, making sure to stay in view and get as much screen time as possible.