Oh god, it's one of those story "ideas"... 

Okay, yes, it's the "Willy Wonka but with the characters swapped out for characters from a different series" cliche. It's overdone in the worst ways, but every so often I indulge in it because it's still possible to have fun with it. I will however omit that bizarre obsession with Violet's clothing. Yes, it's rather obligatory to have someone become a blueberry, but you don't need to make it THAT obvious. 

And even though this has the same set up as the Wonka story we don't have to do it word for word, or use only the punishments from the story. We can get creative with it and make our own things. Like gum that makes helium when you blow into so that you can turn it into a balloon, nuclear pop rocks where one pebble has the same amount of fizz as ten bags of normal pop rocks, marshmallow paste so potent that putting a drop of it in a vacuum chamber could make 50 bags of marshmallows, etc. Hell, why use a three course gum when they could drink blueberry soda in a dedicated brewery in the factory? Wonka's candy and candy making methods are insane to say the least, so why limit ourselves to what was specifically in the story? 

The only problem I can find in this is who would be in the place of Wonka, because I am not using the actual Wonka, and we're certainly not using ourselves... I guess it would be an OC made specifically for this role. We'll discuss it. 

As for the five lucky prize winners, one of the will obviously be an alternate version of Chara, because Alternate Universes are totally canon, and Toriel, and we'll decide who the other four will be. Chara's role in the story is the opposite of Charlie's where instead they get everyone else in trouble by tricking or sabotaging them. If someone fell into the chocolate river it's because Chara pushed them in. That said, Chara's love of chocolate could easily play a role in this, namely for that promised life time supply of chocolate. 

Fetishes will definitely include candy tf, inflation, expansion, blueberry, stuffing, and weight gain.