1. The most popular Halloween candy in America is Skittles.
2. During the eight weeks leading up to Halloween, consumers spend $4.6 billion on confectionery products.
3. Donna Arnett, head of the department of epidemiology at University of Alabama’s Birmingham School of Public Health, estimates the average American kid eats anywhere between 3,500 and 7,000 calories.
4. Candy corn used to have a different name, Wunderlee Candy Company, began mass-producing the sweet in the early 1900s, originally calling it Chicken Feed.
5. In an animal study, University of California-Los Angeles researchers found that fructose—a key ingredient of sugar and high fructose corn syrup, found in almost all Halloween candy—can interfere with communication between neurons and affect memory after an injury.
6. The candy manufacturer Mars started distributing mini candy bars in 1961, specifically targeting trick-or-treaters, and coined the phrase “fun size” in 1968.
7. Tootsie Rolls were included in soldiers field rations during World War II to give American troops “quick energy.” 
8. Kit Kat bars were introduced in Japan in 2000, and now more than 350 flavors of Kit Kats are sold in that country.
9. Chocolate can stay good for six to eight months past its expiration date if it’s kept in a freezer.
10. Halloween candies such as Brach’s Dem Bones, Chicken Dinner Candy Bar, Hershey’s S’mores, Cookies-n-Cream Twix, Astro Pops, Nestle Wonder Balls, and almond and dark chocolate M&Ms have been discontinued.

Source: https://www.rd.com/list/halloween-candy-facts/