Opening there from Kinnikuman Nisei or Ultimate Muscle as it was known in English.
I've not actually seen the anime, however I have read some scanlated chapters of the original manga which I enjoyed greatly. And when I was a kid, my brother and I collected these:
M.U.S.C.L.E. – Millions of Unusual Small Creatures Lurking Everywhere.
This is what (briefly) passed for Yu-Gi-Oh cards when I was a kid! In fact looking at that packaging and remembering that the toy shop I got them from used to stock Games Workshop and TSR stuff too, these were probably my gateway drug into Warhammer.
Yes, in the Eighties Mattel took toys based on an unreleased manga and anime show, gave them entirely new names and launched them to little success in the UK and US. What a masterful money making scheme.
Actually from my experience, it was not unusual to run into toys unknowingly based on anime and manga during in the 80s.
I recall being about 8 and my friend, William, having a robot with removable magnetic arms and legs. This I would learn many years later was Steel Jeeg, a Go Nagai creation. Also one Christmas, “Santa” had left plastic model kits of oddly designed animals for my brother and I. I have no idea what they came from, but the memory of them came flooding back when I first saw the typical comedy manga octopus that appears in an early episode of Urusei Yatsura. And finally, about 15 years after I was given it, the metal robot keyring I had turned out to be UFO ROBOT GRENDIZER, another Go Nagai creation. In many cases these would have been licensed toys from continental Europe, where the shows had been dubbed and broadcast, that had somehow found their way to the UK. Usually in seaside towns.
Kinnikuman starts off as a broad parody of superheroes and Ultraman in particular, but then as Shonen Jump strips tend to do, once it's position was secure if veers off in a different, if not wholely unrelated direction.
This went on for sometime, leading to great success in Japan. France and Catalan. But all the English speaking world saw of it was the aforementioned pink plastic toys.
The year 2002, and the sequel to Kinnikuman, Kinnikuman Nisei is adapted into in English and called Ultimate Muscle, in reference to, well you know.
Now, a number of characters have kanji on their foreheads. The writing of meat on peoples foreheads in the overlooked show Sexy Commando is, I understand, a reference to Kinnikuman. Well with 4kids and Fox looking after Ultimate Muscle, those kanji had to go! The show looks to have been a reasonable success with the US adaptation running to 3 seasons, with new episodes ordered by the US distributors themselves.
The way Kinnikuman Nisei got adapted is somewhat odd, as rather than being aimed at kids as it's progenitor was, it's actually aimed at the men who grew up reading the original Kinnikuman. And as such rather than running in Shonen Jump, it runs in Weekly Playboy, which I'm guessing is the Japanese equivalent of Nuts or Zoo. The anime wasn't based on the actual Kinnikuman Nisei strip itself, but from a spin-off of the spin-off that was aimed at kids and ran in V Jump, a video game magazine.