1 Ponsonby: What are these “Monkees” you’re talking about?
2 Mate: Davy Jones is their leader.
3 Mate: I first heard about them from advertisements. They grow rapidly when immersed in salt water.
4 Ponsonby: Ah! Sea-Monkees.

Sea-Monkeys is a brand of small aquarium pets, which are actually a species of brine shrimp. The creatures are capable of living for long periods as cryptobiotic eggs, remaining in a dormant state while dry, and hatching when immersed in water of an acceptable salinity. As dry eggs brine shrimp can lie dormant for decades at least while remaining viable.

The American mail-order marketer and general all-round charlatan Harold von Braunhut (1926-2003) established a mail-order business selling small packets of dried brine shrimp eggs under the trademark of "Sea-Monkeys". He advertised them heavily to children in comic books of the 1960s and 1970s. If you ever read any comic books of the day (as I did), you'd be familiar with the ads, which look something like this:

The stylised drawings of the Sea-Monkeys look virtually nothing like the tiny and disappointing brine shrimp that hatch from the "Instant Life!" sachet. The "year's supply of food" that some ads promised was just a few spoons of yeast - all that's required since the shrimp will happily graze on algae that grows naturally in their bowl. If you wanted to keep them healthy and happy, however, the ads encouraged you to buy supplementary sachets of stuff that also wasn't needed.

It was basically all a big scam, albeit one with just enough science behind it to get von Braunhut a patent on the mixture of chemicals and eggs in 1972.

Not to be outdone by himself in the scam stakes, von Braunhut was also the inventor of an "improved" version of the infamous "X-Ray Specs" that were also advertised in comics books of the day. These were advertised with an illustration of a man wearing the specs, looking at his hand, where the bones are drawn to be visible, while nearby stands a curvy young woman, topped with the slogan: "See the bones in your hand, see through clothes!" Just the sort of thing a comic-book-reading boy would instantly want to nag his parents for a dollar to send off the mail order coupon to get.

Again, of course, this was a scam. The specs were essentially just two cardboard "lenses" with small holes in them. Between layers of cardboard were either feathers (in the earliest examples) or diffracting plastic. These produced blurry images of whatever you were looking at, slightly misaligned so that the overlap was not exact. When viewing thin objects such as fingers, this produces the visual illusion of a thin solid material surrounded by a halo of partly transparent material, which might generously be considered to resemble an x-ray of the bones within. Looking at a person, you would see a slightly thinner solid person surrounded by a semi-transparent halo - certainly not the naked ladies implicitly promised.

Von Braunhut's Wikipedia page contains this gem describing him:

Braunhut used comic book advertisements to sell an assortment of fraudulent products.

Another product was "Invisible Goldfish" - which were simply imaginary pets, although "guaranteed" to remain permanently invisible.

Lest these examples of his get-rich-quick-at-the-expense-of-disappointed-kids schemes persuade you into thinking of Harold von Braunhut as an exemplary paragon of humanity, he's also notorious for having been born into a Jewish family, but later rebelling against Judaism, adopting the "von" in his name to sound more Germanic (he was born Harold Nathan Braunhut), and associating closely with white supremacist groups including the Ku Klux Klan and Aryan Nations.

Sometimes you just can't tell, can you?