After finishing The Machine, I installed the Expansion Pack.
For some reason, I believed it to be a selection of the very best community levels of 2007 (I probably thought it was the Third Party Pack, I guess).
I started playing A Strange Dream and was like "Woah! Where did all those new enemies come from? I can't believe a fan did all this by themselves." Then I fell into the beloved Chomp trap... and nearly had a heart attack (and that was just the beginning… Yes, I'm referring to elementals).
Since I had not yet found the boundaries of the level, I kept going right... Again... Again... And again. I thought "Man, this level completely dwarfs The Machine, look at this! You could get lost in here."
Then I
finally realized, "Wait a minute. I'm at the eskimos... again? Wat. What kind of sorcery is this?" And that was the first time I experienced a seamless warp.
After some time, I realized it was made by Nifflas, and that "new" enemies are in the editor by default.
Then (after months), in my second playthrough, I talked to the cute bird circle and realized it had a secret ending, just like The Machine, and also an OST player.
And finally, when I learned how to use Ego's editor, I also found secrets (the cat and the sheep. I wish I had found them in-game though), and realized there were like a thousand different ways to beat it, due to the duplicated power-ups.