I's in the fortress scene near the end (around the time they do the white-laser-beam-out-of-the-finger bit) I'm surprised nobody has caught it.

While one of the other characters is speaking, the guy who plays Non looks offstage and apparently notices something wrong. He raises his hand to point and opens his mouth to say something but stops himself. Maybe he didn't want to be the one to ruin the shot or maybe he decided there wasn't a problem, so he closes his mouth suddenly, and continues his point motion up to his face and scratches his nose (or was it his chin?). I don't know if they crop it for tv, but it's on the VHS for sure.

Watch for it, it's pretty comical.