Hear me out: So when I made these somewhat official designs of the demons, I had already dabbled on posting some of their stories in Tumblr. Stuffy's is one of em. While the comic that debuted him is still relevant, his design from then has changed drastically, so I think I'll just copy/paste his more fleshed out backstory here:
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This is the story about a family created by a demon.

Florencia was a girl born from a rich investor and an immigrant maid. She was taken in by her father, but largely neglected; a secret to keep locked upstairs.

One day, for a sister of Florencia’s birthday, the family went to watch a circus. Florencia, of course, stayed behind.

The family never returned in one piece.

Florencia was alone. Ten years old, she knew she was in trouble, but she could do nothing. Servants left, distant family members would come only to dispute over assets in the office. Though her father made it so his children would get all his possessions, she was never brought up as a candidate. She didn’t want money or possessions, she just wanted a home. But knowing the adults, they would rather kick her out the second they claimed the house, than have to keep her around.

At night, she noticed a voice from the bottom of her bed. Always soothing her. Always making jokes. Always promising it would be okay. If she made a deal... She was scared to even look down, and would try to ignore it. But one particular night, her uncles weren’t leaving. They were coming to a conclusion, and she knew. She needed to act.

She gave into the deal, and the figure showed itself. It promised it would only take what could be spared. All it needed to seal the deal was a body. The girl's teddy bear would do for now.

With the ritual done and his soul bound to stuffing, something peculiar occurred. She couldn’t let go of the bear. She couldn’t move her body at all.

The demon had actually possessed her. And, using her, 'she’ moved to barge in to the office and demand they leave. The men laughed.

'She’ walked over to father’s desk and took out the pistol from his top drawer.

'She’ wouldn’t ask nicely again.

They moved closer, trying to take it away. She shot an uncle’s fingers off. That finally brought them to their senses. She wasn’t going to leave.

“That was your second warning. You may not believe it, but I am a quick shot. I will kill you. This is my property and you are no longer welcome.”

They were outraged. The nerve of this girl, claiming this house! 'She’ looked at the only lawyer in the room, straight into his eyes.

“I know my father’s will like the back of my hand. You ingrates will destroy his legacy given the chance. This is why he never mentions any of you. Now leave, or else, by law.” 'She’ smiles. “I can commit murder.”

They left but promised they would return back for revenge. Finally, with everyone gone, the demon let go.

Florencia fell to the floor. She couldn’t believe what had transpired. She was…

She was glad she made the deal.

This wasn’t over, he assured her.

She needed allies. Staff. To continue her father’s business. He would make sure she would thrive, and she eagerly held his body close. She welcomed all his reassurances.

~~~

I think I'll continue this story in another post..... because its so long, and I have more art that better suits this next part.