Dib uses one of Professor Membrane's inventions to try to see into another dimension and inadvertantly opens up an unstable gateway into the other dimension…which happens to be a nightmare world inside his freakishly large head. While fleeing the nightmare monsters in his own head Dib manages to pull Zim in and they're forced to work together to evade the monsters and escape.

The nightmare creatures were very well done - they were the perfect mix of horrible and creepy and still somewhat human and hilarious. I also liked the way that the creatures were forced off to an even worse place when they failed Nightmare Bitters (with their hats and coats and a final wave…)

My Favorite Moments:

I enjoyed all of the big-head humor in this one a bit too much - I have a large headed friend who is doomed to receive taunting sound clips from this series and especially this episode for the rest of his unnatural life.