Ms. Karla Ebbledeen waits with a calm patience just behind her front door, wearing a rather revealing witch costume that she's held onto for years. A bowl with a few pieces of candy in it sits on a small stand next to her; for the start of the night, it's rather empty. She smiles, though. Tonight is her favorite night of the year.
She watches as a child no older than 10 approaches her door, wearing an adorable little Eevee costume. Karla's smile grows across her canine face as the vixen awaits her first visitor. The small, faint knock of the little girl finally comes, and the woman opens her door.
"Trick or treat!" the girl says enthusiastically, holding out a pumpkin-shaped plastic pail with a few small pieces of candy in it.
GRWWWRRLLLL
Ms. Karla Ebbledeen's home is on a street that's rather busy and one parents are known to trust. It's not unusual for them to wait in the car and let their little ones visit an entire block at a time, and indeed as the fox had hoped, nobody is attending this little girl.
The fox drags the kid inside and closes the door quickly, stuffing a hand over the girl's mouth to muffle any cries for help. She wrenches the candy basket away with her free hand and sets it beside her own candy bowl before pulling back the hood on the little one's costume and lifting her up to stuff her head into her maw. 
OMNPHF
With her ravenous maw muffling the child's desperate screams of protest, she's able to slowly work the costume off of her as well as what little she's wearing underneath. Karla tosses the girl's underwear to the side and sets the costume on the ground in front of her.
With a single, powerful gulp, she swallows the child down. The helpless kid screams and cries uselessly inside of her as she sinks into the fox's stomach, squirming uselessly and making a few small bulges that move over her abdomen.
ULP GRRRRRGGLE URRRRRRP
Karla unbuckles the tight witch costume to let her enormous gut bulge out of it and wriggle around more freely. She then takes a seat in a chair she'd prepared near the door and lets out a contented sigh as she enjoys the little one's useless struggles.
"Oh, goodness... Huff... I've been waiting for this~" Karla squeezes her gut with both arms, making the child scream louder, "You stupid little pieces of meat just walk right up to the door, and you bring free candy with you~"
GRRRRGLLE CHURN GLORP
The little girl's screams gradually die out, either too exhausted or too melted to yell any more, and her struggles grow weaker and weaker until she barely makes a bulge on the cruel woman's gut. With another huff, the fox gets out of her seat and watches through the door's window.
A small boy is approaching in a racecar driver's outfit. His parents watch from the driveway.
"Trick or treat!"
Karla drinks in the uncertain look in the boy's eyes as he stares up at her massive, bulging gut and watches her lick her lips as she stares hungrily down at him. In view of his parents, though, that's all she dares to do.
"Here you go, kid~ Have a lovely Halloween, and don't get eaten by any nasty witches!" she says as she drops a single pack of bite-sized Twizzlers into his pail. She never liked those, anyway, so she can part with them.
GRWWRRGGGLLLE
The boy leaves with one last uneasy glance back at her, and she shuts the door. Her insides are feeling very heavy now with the girl she'd eaten.
Karla turns her porch light off so she won't be bothered while she takes care of the next part of her plan. She takes the discarded clothes of the former trick-or-treater and walks into her bathroom.
The fox ties the arm and leg holes of the girl's costume shut before placing it over the edge of the tub. Then she gropes her own rock solid cock a few times as she gives the girl's underwear a quick sniff and sets them over the edge of the sink for later. She then quickly undresses.
Now nude, with her gut sagging heavily, smooth save for a few bumps of bones packed in with the mush,  she steps into the tub. Karla squats down and holds out the girl's costume behind her rear then begins to push out the little one's remains.
FBLRBFRHFBLRFFBLL SCHLORP
A massive log is pushed out of her and into the costume through the head hole. The enormous mound of shit is caked with countless little bones that protrude out of it. It slops down into the costume and fills out the bottom of it with a few stray bumps of misplaced bones.
PFRRRRFBT FBLRRBFBLRLL SPLFBLFBLTFFLLL
The scat continues to pour out of Karla's backside into the costume, ribs, vertebrae, and all spewing out from her backside in the slurry. It packs the costume full much in the way the in-tact child had filled it before. Finally, with a grunt of effort, the little girl's skull is pushed out and lands at an odd angle in roughly the spot where her head would've been.
GRRRNT HUFF... SBFHLFPBT
Karla pants for a moment before setting the costume down in the tub, lifting up the hood that the skull caught in and leaving it to rest for now. She takes only a few seconds to admire her victim and snap a photo to remember her by before slipping her witch costume back on without so much as wiping her rear end. Karla returns to her front door.
She flips the porchlight back on and is delighted when another knock comes sooner rather than later.
By the end of the night, her bowl has been filled with candy several times over, her collection of victims' panties has grown significantly, and her bathroom absolutely reeks of former children.
Ms. Ebbledeen has had a lovely Halloween.