Digital Devil Story: Megami Tensei

Based on a series of Japanese horror novels, Megami Tensei kicked off the long-running RPG series of the same name. When a boy-genius computer hacker figures out a way to summon demons from folklore and religion via the power of COMPUTERS, things go utterly pear-shaped and he has to team up with a friend from school to stop demons from taking over the world! Naturally, this is done by chatting them up and convincing them to fight on his side.

Easter Egg
One particularly strange random monster encounter in the game is a BULL monster, flipped upside-down, with the word "BUG" crudely typed over the sprite. Surprisingly, this is actually deliberately included, as there's an easter egg tied to it!

When you encounter this enemy in battle, press and hold A + B + Left + Down on the second controller, then select "AUTO" to start the automatic battle mode. The generic message about your character fighting the monster ("ナカジマたちはたたかっている. ", or "Nakajima and the others start fighting."), will change to the secret message: "カブちゃんはDEBUGをはじめた. ", which translates to "Cabu-chan begins debugging.".