Some candies last the test of time, their combinations and ratios of chocolate, caramel, peanuts, raisins, crunch, and other ingredients just as popular with the next generation as the one before.
Sure, there may be tweaks to the original formula, new or more involved advertising campaigns, and wrapper redesigns — candies can even be given a fresh look with new colors, as with M&M's. Some are so successful, become so iconic, that the idea of them going anywhere seems impossible. Take, for example, Baby Ruth bars. Whether you want to believe they were named after the Yankee slugger, or President Grover Cleveland's daughter, you can't disupte its staying power — it has been around since 1921. But there's also a Reggie! bar for every generation.
Where some candies are so sucessful that they get new versions of the original, iterations with peanut butter, caramel, and mint, other candies don't have the same staying power. Sometimes, they disappear because of changing tastes. Sometimes, the celebrities and special occassions used to name, package, and sell candies aren't powerful enough to carry them far beyond the staying power of those cultural reference points.
Some names seem like they may not have been such savvy ideas to begin with. Ever heard of the Air Mail bar? In 1930 it was named for a the first airmail flight in America. Like the actual flight, which wasn't successfully completed, the candy bar didn't have a long run. Then there was the Sal-Le-Dande, a candy bar named after a stripper. The Vegetable Sandwich bar and the Chicken Dinner bar seem like similarly bad ideas. Others, like the Fat Emma and the Seven Up, may have been discontinued, but inspired other successful bars or found staying power in other products.
These tidbits about extinct candy bars come from Uncle John's Bathroom Reader, bringing you a list of long gone sweets from candy bar historian Dr. Ray Broekel.