If you were a kid in the 50s you read comic books and the ads they carried for magical products like Sea Monkeys, X-Ray Glasses, the Charles Atlas Fitness Program, the Ventrilo Voice Thrower, the Spy Pen Radio. I wanted all of them - desperately. My mother would not front me the bread to buy them and at the time I felt deprived.
Years later when my sons were little I bought them sea monkeys and, to put it mildly, they did not live up to the hype. They were creepy little transparent brine shrimp that grew red veins in their backs before one by bloody one they died. My mother was right, they weren't worth spending good money on.
Read a great article about these disappointing products at Collectors Weekly