There are rumors that mixing Pop Rocks with carbonated drinks would cause your stomach to explode. Further, according to playground lore, an overly-cute kid who achieved fame in LIFE cereal commercials had died of this. Why Little Mikey, of all people? Urban legends require victims who are known yet anonymous — the ubiquitous friends of a friend — to lend them a touch of credible realism without allowing for the easy verification of their details.
Little Mikey was a kid known to all other children by virtue of his famous television commercial, yet he was still relatively anonymous — few people (adults included) knew his real name, and his non-appearance in any public role subsequent to his well known LIFE commercial could therefore plausibly be attributed to his untimely demise. (Contrary to the rumor, John Gilchrist, the lad who played Mikey, not only survived his childhood un-exploded, but is now an advertising-account manager for a New York radio station. And no, that’s not him in the new LIFE commercial; that’s Jimmy Starace.)
The company stopped marketing Pop Rocks around 1983, and this is often pointed to as "proof" that the candy was so harmful it had to be pulled from the shelves.