You've led a normal life-until this morning, that is! You wake up to discover the world is under attack! Evil Mushroom Men from the far reaches of space have come to conquer our world! What vile plans do they have for us, pitiful mammal?

It's up to you to decide how you cope with this sudden attack by alien fungi. Choose to be a hero, a villain, or just some schmuck trying to survive and not get fried. Rescue your neighbor, or leave her to her fate. Try to escape the alien onslaught, heroically seek to end the threat they pose, or turn traitor and lead the Mushroom forces to victory.

Remember, mammal, the Fate of the World is in your hands! Dum dum dummm!!!

Invasion of the Mushroom Men of Planet Y! is a goofy, light hearted visual novel. In addition to making choices to decide where the story goes, a few key choices are dependent on a random luck factor (these points are heavily hinted at in the text).