A frustrating, yet decent, game ...
So, the gameplay is like this:
You walk around killing random enemies, and go into doors. These doors are either empty, or they contain the bosses. You have to kill all the bosses in the level in order to get the key so that you can go to the next level. These bosses are quite unique, and most of them have something funny to say before they try to kill you. When you play as Mark, he uses his bat to hit the enemies. To transform into the eagle/alien, there's a power up that resembles a pill. And when you're that monster (Bert), you can shoot and you can also fly.
Graphics are not too shabby. It's a game about monsters, so it looks dark and gross most of the time. The sound isn't very good. I can't recall any of their songs because they're not memorable. The sound effects aren't that good because, well, there's not much of em.
So, aside from the frustrating gameplay and weak story, Monster Party is still a decent game. I enjoyed the bosses and it's one of those games when it feels like you achieved something when you beat it because it was so hard and annoying (I, as a kid, couldn't beat it) With that in mind, try out the game.
It's a Monster Party and you're invited :D