Best sci-fi TV revealing mistakes of 1992

The Cure - S1-E9

Revealing mistake: When Rogue puts the dome in place, if you look closely you will see that the dome is resting on thin air (note that you can see the sky through the platform she sets it on, and when she sets it down, the underside of the dome is visible). (00:06:15)

Phaneron ★

The Tale of the Dream Girl - S3-E10

Revealing mistake: A kid running through the bowling alley moves aside to let Johnny, who is a ghost only his sister can see, pass by.