[pak]

I seem to remember some Batman cartoon where Batman realizes he's in a dream because letters shift around oddly while he's trying to read something.

Indeed, I remember from my own dreams that text and numbers behaves oddly (disappears/changes when you look around).

I've also heard this technique is used by lucid dreamers (http://en.wikipedia.org/wiki/Lucid_dream) to figure out that they're dreaming so they can begin to take control of the dream.