The Conspiracy: The secret ingredient that makes Willy Wonka’s chocolate so good is actually children.
The Evidence: None of the children are seen again at the end of the movie. They could be back out in the real world living their lives or… The tube that sucks up Augustus Gloop is far bigger than it needs to be to syphon chocolate. Violet becomes a blueberry, a sweet ingredient. Mike TV is shrunk down literally to “bite size”.
Further evidence lies in the book (Spoiler if you plan to read). There is a sixth golden ticket in the book which goes to Miranda Piker. She meets her end when her and her father fall down a chute into a powder-grinder. Afterwards, the mother actually accuses Wonka of intentionally killing them, to which Wonka replies, “Of course. That’s part of the recipe.”