Slim Goodbody had all the superhero staples: a secret headquarters, a robot sidekick, and an identity he kept hidden behind a shimmering outfit. He even had a spandex costume that materialized behind a puff of smoke when he was called to action—though it’s safe to say he was the only superhero of his time that resembled a page from an anatomy textbook.

The main mission of the "Superhero of Health" wasn’t fighting bad guys (though he did that as well); it was teaching kids to understand and care for their bodies. John Burstein, the man responsible for bringing Slim Goodbody to life, didn’t initially intend to make a career out of the character. "When I was younger my goal was to be a Shakespearean actor," he told mental_floss. Burstein studied drama at Hofstra University, and in 1973 the 23-year-old took a job as a performer aboard the Floating Hospital in New York City. Playing guitar in front of audiences was something he had been doing since age 13. Using his musical talents, he was able to present health concepts to children in an engaging package.

The response to his songs was so positive that Burstein felt inspired to devise a character to go along with the act. "I wanted to do a body suit but I didn’t want it to be gory,” he said. “I wanted it to be superhero-esque." To create the style he was going for, he started with a leotard purchased from a dance supply company. An artist painted organs onto the suit (with him in it) and set the design through a special heating process (without him in it). The result was Slim Goodbody, possibly the only character in history capable of pulling off the skinless look.

From there, his one-man show moved beyond the Floating Hospital. He began performing at local schools, and in 1976, he landed the gig that would launch his television career. On Captain Kangaroo, Burstein played Slim (alter ego: Chief Hale and Hearty) in biweekly installments of "The Adventures of Slim Goodbody in Nutri-City." Slim Goodbody and his friends fought to uphold the laws of good health and protect the citizens of Nutri-City from villains like the mind-controlling mad scientists Sarah Bellum and Lobe. His four-year stint on the show proved to viewers and networks alike that health-centered programming didn’t have to be bland. Burstein’s work caught the attention of PBS, and in 1980 they offered him his own series titled The Inside Story With Slim Goodbody.

If Captain Kangaroo introduced Slim Goodbody to kids at home, Inside Story brought him into their classrooms. Teachers loved the show for its information-packed episodes told through catchy musical numbers. But unlike other mnemonic devices meant to remind students which parts go where, the songs in Inside Story made biology feel personal. During "The Smart Parts: The Inside Story of Your Brain and Nervous System" Slim walks through a tinsel-like webbing of nerves, singing: "You couldn’t laugh, read, think, dance, dream, have fun, or sing. Without your brain you couldn’t do anything."

And during the tune "Down, Down, Down: The Inside Story of Digestion," he tells the viewer: "When you were a baby your body was smaller, now you grow bigger and very much taller. Because your body takes food you chew and changes some of it into you." Slim was the face of the show, but by placing the wonders of the body center stage, any kid watching could feel like they had a starring role.

In addition to Inside Story and Captain Kangaroo, Slim Goodbody made appearances on Nickelodeon, Good Morning America, The Richard Simmons Show, and various other talk shows. By 1985 he told The Morning Call that "millions, maybe tens of millions" of children knew him by sight.

Even after making it big on TV, John Burstein never abandoned Slim's live performance roots. Over the past four decades he’s played the character everywhere from school assemblies to symphony shows. The 66-year-old continues to get on stage today, albeit much less often than he used to (for him that means 10 to 12 shows a year). He still performs to sold-out theaters of students, thanks in part to the teachers who grew up watching Slim when they were kids.

Burstein’s act has evolved since the 1970s: The visuals he incorporates into the show now include computer animation, and his songs have been remixed to sound "a little hipper." His body suit, originally a glorified art project, has been upgraded several times over the years. Slim’s latest outfit comes from the same costume designers behind Star Trek: The Next Generation and is worth roughly $4000.

One thing that hasn’t changed is the message Burstein hopes to impart on his young audience. According to him, the purpose of Slim Goodbody is to create "some positive feeling about what it means to be a human being." When asked what he wishes kids to get out of his shows, he said, "I hope they take away a sense of how wonderful they are, how wonderful the body is, and that possessing a body that’s so wonderful means there’s something marvelous about themselves."