I think the first 'demo' (multipart) and specifically done for copyparties are from 1987.
I remember something of that period with exciting effects and not only because there were boobs visible (double o, not a typo)
.
Some parallax screens moving around, with multiscrolling and sampled audio.
But now I do not remember the names, neither of the programmers nor of the production.. I should search on pouet.
EDIT: found!
http://www.pouet.net/prod.php?which=4445