There are two single-frame flashes of Dark Stryker before Neil Stryker takes the potion. One when Neil wakes from his dream and the other when Neil is strapped to the laser table.
When Neil Stryker looks out the window, the four cult members out there in the garden are the directors; two of Neil Taylor and two of Rob Taylor, using split screening.
The alternate ending featured on the DVD contains many single-frame images, some of which have no real connection to the movie; one is a picture of Rob Taylor as a child.
The movie has an original ending that was scrapped because it was too dismal, but it is available to watch on the DVD.