When Gleek leads the SuperFriends to the small cave the Wonder Twins went into, it looks like Batman says, "Well, let's take a look." The voice heard, though, is Danny Dark (Superman).
Malhavoc: Fools! You think you've escaped me, but you've only succeeded in sealing your fate. That passage you've entered is the cave of the three deadly tasks. No one can survive it (evil laugh).
This episode is very loosely based on the novel trilogy, "Lord of the Rings" by J.R.R. Tolkien.