Be Cool, Scooby-Doo! - Season 1 Episode 7 -

To solve the mystery of a creepy Crystal Crawler - a bat-like cave monster - the Gang must venture into the Crystal Canopy - a labyrinth of intricate crystal formations. To make things worse, they can't speak a word while in the Canopy, because even the slightest sound will bring the crystals crashing down around them!