Continuity mistake: The size and shape of the stain on Nicholas' shirt after he falls into the spillage, changes.
Audio problem: Towards the end of the episode just before Grace turns out the lights, Nicholas says "Ugh, now what?" but his lips are not moving at all, even with his head turned.
Answer: According to all online sources I found, yes, this really was R.L. Stine.
raywest ★