Was that the one when their pre-chosen dreamsign was a full moon and they kept seeing it everywhere, so they were still dreaming and couldn't wake up? I'm not really a trekkie but I remember that one. The Māori dude with tattoos could WILD at will so he did to help the crew, and he said if we see the full moon, we know we're still dreaming. Of course when they think its all over, they see a moon somewhere and realise they're still dreaming.