Lol I found out that the demo levels are even in full secret files, but because I didn't play through it yet, I didn't know, the ghostly antic level is there, :P.

By the way: Is there some level using the hidden sprites etc. somewhere for download?
Anyway also these passwords you get after finishing secret files and christmas chronicles, but there is no use for them as those sites are not existing anymore.
What was reward then?