As the goons arrive at the farm building with Jeff, the door that they walk through changes.
At the start, when Cynthia's veil is blowing into Marty's face, he is seen brushing it off him by moving his head.
A double used for Jeff during his fight with Hooper and Grant in the Seaton mansion.
After the two villains throw Geoff into the river, Marty's reflection can be seen in their driver's door as they drive away. Marty is supposed to be an invisible ghost.
Reflected in the driver's door of the goon's car before they throw Jeff into the river.