Monster Party

Not to be confused with Great Britain's Official Monster Raving Loony Party, Monster Party is quite possibly the most bizzare NES game ever made.

Plot (or what passes for it)
A young boy (roughly 12 years old, by the look of it) named Mark is walking home (from what must be a baseball game of some sort, since he's carrying a baseball bat), when he is visited by a bird-like monster named Bert. From what I can tell, Bert's home dimension is being invaded by evil forces, and for some reason, he's chosen Mark to help him. Mark and Bert must journey through the monster dimension, fighting numerous creatures, including a host of weird bosses ranging from a bubble-spewing pitcher plant, to a giant flying breaded shrimp who mutates into various fried foods as you fight him, to a pair of dancing Japanese zombies, and even includes the Grim Reaper.

Gameplay
The gameplay is fairly basic sidescrolling fare, really nothing to write home about. Mark journeys through the frequently surreal terrain of Monster World, fighting off baddies with his baseball bat. As mentioned above, there are frequent fights against strange bosses. After beating all the bosses (or maybe it's one specific boss, been a while since I played this), you get a key that you use to open the door at the end of the level and advance to the next.
Adding a bit of variety to the gameplay is the fact that Mark can deflect enemy shots back at his opponents (essential for beating some bosses). Also, if you pick up a special pill power-up (remember kids, Winners don't use drugs! So don't try this at home), you can transform into Bert for a brief period of time, and shoot lasers.

My Thoughts
I think the major appeal of this game lies not in the gameplay (definitely not the gameplay), but in the surreal images, enemies, and dialogue (the fried-food boss shall go down in zany video game quotes history for greeting you with "Look out baby, here I come!") that so frequented games in those days. Because without such elements, I think Monster Party would undoubtedly have slipped into the same pile of mediocre Nintendo games that so many other titles did.