lvl 30 - type idclip and with noclip mode run into demon's head - you will see what really are you shooting rockets at
lvl 32 contains hang Commander Keen dolls
lvl 30 - try to record the speech demon has when you enter level and then play it backwards
idchoppers - chainsaw and quote
as much as i remember from easter eggs - its about 9 months i played it last time