On: Tim Ferris: Beginner's Guide to Lucid Dreaming

[WilliamLP]

But it helps if you're visited by aliens, ghosts, or demons, because you can mistake that for sleep paralysis, making it not very frightening.

[DougWebb → WilliamLP]

The trick is to ask them to read something twice; if it comes out the same each time, they're really there. Otherwise you're experiencing sleep paralysis. Or they're just messing with you.