i actually remember reading an article about Centipede’s backstory, once. according to an official comic book that came with the original console version of the game, it’s actually kinda messed up.
you’re an elf, who lives in the forest with your friends, the spider, the flea, the scorpion, and the centipede. for some reason, an evil wizard shows up and wants to steal your magic wand, so he uses his powers to mind control your friends and make them attack you. you spend the rest of the game fending them off, turning them into toadstools because you don’t want to kill them. but of course, as you fight it’s essentially guaranteed that you’re blasting away plenty of toadstools too, so no matter what you’re killing your brainwashed friends.
and the worst part is that there is no ending. you never fight the wizard, you never get to change your friends back, you just keep killing and killing until they tear you apart.

to put it like Cracked.com: Centipede was the very first survival horror game.

Only an unlucky few were left alive to hear the final burst