Muggles' Guide to Harry Potter/Magic/Skiving Snackbox

Overview
Skiving Snackboxes, a creation of Fred and George Weasley, are a portable way of escaping from ("skiving off") classes or other duties.

Extended Description
As would be expected of Fred and George, one of the first things they invent for their joke shop, Weasleys' Wizard Wheezes, is a way of escaping from classes. Skiving Snackboxes, which are under development throughout Harry Potter and the Goblet of Fire and Harry Potter and the Order of the Phoenix, is that escape. Typically, a Skiving Snackbox is a candy with two colored ends; eating from the one end will bring on some sickness, eating from the other end will cure it. In order to secure the fastest escape from class, illnesses caused by Skiving Snackboxes are designed to be dramatic.

Several different Snackboxes are mentioned in passing:

Puking Pastilles
Puking Pastilles cause repeated projectile vomiting; they are the first of the Snackboxes to be mentioned and also the first to be perfected. We see Fred and George demonstrating these in the Gryffindor common room in Harry Potter and the Order of the Phoenix..

In Harry Potter and the Deathly Hallows, Hermione uses one of these to incapacitate Ministry employee Reg Cattermole, as part of the preparations for invading the Ministry.

Fever Fudge
Fever Fudge causes a very high fever; a prototype, tested by Fred and George, has a side effect of giving them large, pus-filled boils in a very private place. A later version which makes use of Murtlap tentacles seems to resolve this problem.

Nosebleed Nougat
Nosebleed Nougat results in a sudden and dramatic nosebleed.

When Katie Bell is hit in the face with a Quaffle during Quidditch practice and gets a nosebleed, Fred accidentally gives her a Blood Blisterpod, one of the raw ingredients, and as a result Katie nearly falls off her broom from blood loss and has to be taken to the Hospital Wing.

They are eventually perfected and are mentioned in Harry Potter and the Half-Blood Prince as being the most popular of the Skiving Snackboxes; at the time of Harry's visit, "only one battered box" remained on the shelves.

In Deathly Hallows, Ron uses one of these to incapacitate Ministry employee Runcorn, allowing Harry to impersonate him.

Fainting Fancies
Fainting Fancies cause the person taking them to pass out. Hermione stops Fred and George from testing these on first years only by threatening to write to their mother.

Analysis
Fred and George developed this product independently, but there was discussion of a similar product, much earlier in the Muggle world.

Circa 1960, Mad Magazine ran a feature called "Products We Would Like To See". One of them was "Instant Fink". Description was roughly as follows:


 * Your aunt fixes you up with a blind date, a girl with a "great personality". You know what THAT means, and your suspicions are confirmed when you go to pick her up. She's as big as a bus!


 * But never fear, you have INSTANT FINK! Take one pill, and you'll have all of the symptoms of last-stage bubonic plague!  You can beg off with no hurt feelings!  Symptoms wear off in a few minutes, so you can salvage the rest of the evening.

This would seem to suggest that the idea is one that is fairly common; one wonders why it had not been perfected earlier. Almost certainly, though, it is the technical details that the Twins have perfected, having symptoms be instantly reversible rather than timed, for instance.