User blog comment:Lily8763cp/Random Story - Zombie Journal 1 - The Past I Forgotten/@comment-26593304-20170321020838/@comment-5760976-20170321185327

Shoot, I just noticed that grammar mistake.

Honestly, it's just how my "canon" of it is. Dr. Zomboss makes zombies by taking the dead corpses of humans...and animals to make the animal zombies, and then uses a device that brings that back to life. When he died, some zombies he already made used it on himself, but slightly altered so he'd keep his memories. All zombies have their "human memories", but they're locked away. It takes a lot to have them return, though some are revived with their memories in-tact.

Also, Scientist isn't "mentally wrong", he just really dislikes mostly anything that isn't a zombie, and enjoys their suffering. Which I guess can mean he's mentally wrong.