What Are You Laughing At?

Wiki:

Comprachicos (also comprapequeños) is a compound Spanish neologism meaning "child-buyers," which was created by Victor Hugo in his novel The Man Who Laughs. However, the French writer, Pascal Bruckner, gave only as much credence to the term and practice by saying, "if we take Victor Hugo's word for it."

It refers to various groups in folklore who were said to change the physical appearance of human beings by manipulating growing children, in a similar way to the horticultural method of bonsai – or through deliberate mutilation. Allusion to this myth is common in reference to any group or body who seek to alter the minds of children through calculated manipulation. It was one of many unsavory practices alleged to have been practiced by the Gypsies, who were readily demonized due to their perennial outsider status. It was also strongly associated with freak shows, whose popularity was never harmed by an air of savage mystery.

The most common methods said to be used in this practice included stunting children's growth by physical restraint, muzzling their faces to deform them (compare the sufferings of the protagonist of Alexandre Dumas's The Man in the Iron Mask), slitting their eyes, dislocating their joints, and malforming their bones.

The fantastical and absurd aspects of this myth are illustrated in the descriptions of how comprachicos purportedly created artificial dwarfs "by annointing babies' spines with the grease of bats, moles and dormice" and using drugs such as "dwarf elder, knotgrass, and daisy juice". The superstitution was known to Shakespeare, as Beatrice K. Otto pointed out, quoting A Midsummer's Night Dream:

Get you gone, dwarf;
You minimus, of hindering knot-grass made;

As was common for an outsider-based myth enjoying commodity in the 19th century, the practice also came to be associated with the Chinese by Westerners. The methodology was described through fantastical claims, risible to a modern audience but quite credible at the time, as ranging from the transfusion of animal hide and other exotic surgery to simple deprivation of light, space, and vital nutrition.

Victor Hugo's novel The Man Who Laughs is a horror story of a young aristocrat kidnapped and disfigured by his captors to display a permanent grin. In the novel, Hugo gives his own account of the work of the Comprachicos:

"In China, since time immemorial, they have achieved refinement in a special art and industry: the molding of a living man. One takes a child two or three years old, one puts him into a porcelain vase, more or less grotesque in shape, without cover or bottom, so that the head and feet protrude. In the daytime, one keeps this vase standing upright; at night, one lays it down, so that the child can sleep. Thus the child expands without growing, slowly filling the contours of the vase with his compressed flesh and twisted bones. This bottled development continues for several years. At a certain point, it becomes irreparable. When one judges that this has occurred and that the monster is made, one breaks the vase, the child comes out, and one has a man in the shape of a pot."

The Man Who Laughs on wiki, and on the IMDB