I found an easter egg in the fourth level. There's another one above it that just says "nothing here" but I couldn't get a screenshot and ended up killing myself.
EDIT: Dammit itch.io is being stupid and not letting me post the image. I'll see if I can fix it.
EDIT THE SECOND: Yeah, nope. It keeps saying to please confirm your information is correct and something about a verification, and I can't figure out what it wants me to do. I've looked all over for a verification email or something, but nope. Nothing. I'll just tell you how to find the easter egg. Just keep heading left after loading into the first level. You'll eventually come to some sort of staircase cliff. Just keep using the boxes and stuff there to fling yourself up until you reach the top. You'll find the easter egg there.