Ok, I found out that it IS a sequel.
It's crazy because I played Dr. Lunatic a lot when I was a kid (and I still play it sometimes) and I never knew that it was actually a sequel to an older game.
Btw, this game needs a remaster treatment. 

So, is Dr. Lunatic actually a sequel to this game?
Because it says "Spispopd II: Dr. Lunatic" at the top.