Grandpa's eyes disappear for a few frames when he says "That was awful close, Dinky", seated behind Dinky in his plane.
When Mike puts on his green helmet after telling Henry he has to spend the night in the haunted house, the stripes on his collar disappear for few frames.
Near the end, when Henry gets up from his chair to answer the door, one of the wooden planks on the back of his chair turns red for a few frames.