When we were kids, back when dinosaurs roamed the earth, we believed a lot of crazy stuff. Childhood myths were the playground currency we traded in. Here’s a look back at some favorites.

Sea monkey were magical creatures! The ads, appearing in comic books and magazines aimed at kids, were pretty straightforward: Sea monkeys were a bowl full of fun! They were instant pets! The lady sea monkeys wore pretty bows in their um … hair? Antenna? Your whole family would gather around the fish bowl and laugh at their antics!

Of course, some of us ordered sea monkeys and found out the truth. Sea monkeys were brine shrimp. They were most often a bowl full of dead brine shrimp. They were instant pets if you considered brine shrimp pets. No hair bows were visible on the teeny, tiny heads of the teeny, tiny lady brine shrimp. And your family didn’t want any part of dead brine shrimp floating in brackish water in a bowl on the desk in your room.

Pop rocks and Coke would blow your head off! You remember the urban legend. Mikey, the kid from the cereal commercials, did the unthinkable: He ate a bunch of Pop Rocks, the fizzy candy nuggets, and drank some Coke. The intense mixture of Carbon Dioxide and, well, whatever else, was too much for his still-growing skull. Boom!

Of course, it was an urban legend, even if most of us lived in fear of accidentally mixing the two for years, until the Internet came along and snopes.com debunked the story.

According to snopes, General Foods actually took out newspaper ads around the country in 1979, claiming that Pop Rocks were safe.

If your turn your eyelids inside out, they’ll get stuck that way. This is the corollary to the belief that if you make an especially hideous expression your face might freeze that way.

When I was in second grade, a kid in my class named Lonnie could turn his eyelids inside out. Not through muscle control or anything; he just reached up and, using his fingers, flipped them over. I never tried it; Lonnie’s crazy eyelids freaked me out.

Don’t look now, but there’s something under the bed. At one time or another, all of us believed there was something under our bed or in our closet. A hideous monster ready to drag us under, to some horrible place from which we would never return.

Heck, the Pixar movie “Monsters Inc.” was based on the premise and “Calvin and Hobbes” got a lot of humorous mileage out of that fear.

Curiously enough, of all these childhood myths, “there’s something under the bed” is the only one that turns out to be true.

Ha!

Sometime we’ll explore those childhood beliefs that really, really were true, including using a magnifying glass to start a fire and how you will never, ever, use that complicated algebra formula your teacher forced you to memorize.