Most people have encountered The Addams Family and The Munsters, and quite a few can identify The Gruesomes. Few recognize Mr. and Mrs. J. Evil Scientist. And this seems just a trifle unfair, because they came first.
From a certain point of view.
The Munsters took their cue from classic Monster Movies produced by Universal Studios back in the 1930s. In that same era, The New Yorker began to publish Charles Addams's grim little cartoons. However, neither TV series haunted the airwaves and other media until 1964. Prior to that, Addams' characters inhabited one-panel cartoons. They had no names, and even their specific relationship took time to develop. In her debut, the woman we would eventually know as Morticia Addams appears to have an entirely different husband from the character later named Gomez Addams. One-off characters were commonplace throughout the run. The sinister robed figure who would eventually become Uncle Fester had no clear connection to the others. Addams-related media still hasn't settled on that one. He's been identified at different times as Gomez's brother and Morticia's uncle.
So while Charles Addams's work unquestionably inspired the J. Evil Scientist clan, they are the first named monstrous family about whom specific stories were told. They first appeared on The Quick Draw McGraw Show, October 17, 1959, in the back-up feature, "Snooper and Blabber." This largely forgotten Hanna-Barbera cartoon relates the adventures of a cat and mouse detective team who look suspiciously like Tom and Jerry. The detectives blunder into the family's haunted home in the episode "The Great Diaper Caper." Greenskinned Boris looks like the Addams character who would become Gomez, squashed and crossed with Peter Lorre. He also speaks in a parody of Lorre's voice. Goonda is a greenskinned witch/vampire patterned on she who would be called Morticia. She has a decidedly sinister appearance, and constantly smokes a cigarette in a holder. In some later stories, she appears to have hypnotic powers. Junior looks like a miniature Universal Frankenstein Monster and is incapable of articulate speech. A year later, they returned in "Surprised Party," which identifies them as the J. Evil Scientists1, and "Snap Happy Saps." They turn up to bedevil Snagglepuss as well, in "Fraidy Cat Lion." Goonda has pale white skin in some of these cartoons-- though most TV viewers of the time would not have noticed either way. In their final TV appearance (to date), "Chilly Chiller," they get referred to as "The Gruesomes," and Hanna-Barbera considered giving them their own series under that name. It never made it past preproduction.
Gold Key comics, which had the license to Hanna-Barbera's characters, gave the Evil Scientist Family a place in Hanna-Barbera Bandwagon #2 and 3 (1963). They later published four issues of Mr. and Mrs. J. Evil Scientist between 1963 and 1966, coinciding with Halloween. The Evil Scientists also cropped up as a supporting feature in other comic books based on Hanna-Barbera characters. The comic books develop their world a little. They're shown as belonging to a social organization of Halloween types who hold similar, macabre views. Some stories present an older Junior who has learned to speak. A Frankensteinian butler and a grandmother turn up, showing the ongoing influence of the Addamses. The colorists generally made the family green-skinned, but consistency was never Gold Key's strong point, and their hue varies in some issues.
One would think, with the success in the 1960s of two monster family sitcoms, someone would have done more with these characters. Instead, Hanna-Barbera cloned, stone-aged, and redesigned them into The Gruesomes, and moved them to an old mansion next door to The Flinstones. This family eclipsed the Evil Scientists, and retains greater notoriety despite only appearing twice in the original Flintstones series and almost never in later incarnations.2 Gold Key, meanwhile, developed an in-house creepy family, Little Monsters, which ran from 1964 to 1978-- possibly the longest continuous run of any "Suburban Monster Family" series in any medium.3
The Evil Scientists soon fell into obscurity. Cartoonist Scott Shaw claims that, when he mentioned them to Hanna and Barbera in an interview, not even they remembered them.
1. So is his name Boris J. Evil Scientist? J. Boris Evil Scientist? And why isn't he a doctor or professor? All the best mad scientists, historically, have borne an academic honorific. You could ponder these conundrums, but then, you'd be putting more thought into the matter than Hanna-Barbera ever did.
2. I only know of one TV reappearance, in an episode of The Pebbles and Bamm-Bamm Show. However, they appeared a number of times in spin-off comic books. The Scientists/Gruesomes were redesigned once again as the Creepley Family, who appeared on Scooby's Laff-A-Lympics. A Flintstones TV Movie 1980 showed a different monstrous family, The Frankenstones, move into the mansion next door. Apparently, multiple incarnations of the Frankenstones appeared in Flintstones-related media during this era.
3. To date, DC Comics/Time-Warner, who now own the rights to the Hanna-Barbera catalogue, have left the Evil Scientist family alone
"All in Favor Growl 'Aye." Hanna-Barbera Bandwagon #3. 1963. Reprinted at ComicCrazys. https://comicrazys.wordpress.com/2010/09/17/mr-and-mrs-j-evil-scientist-hanna-barberas-band-wagon-3-1963-artist-uncredited/.
Don Markstein. "Mr. and Mrs. J. Evil Scientist. Toonopedia. http://www.toonopedia.com/jevilsci.htm.
Bob Nelson. "Mr. and Mrs. J. Evil Scientist/Gruesomes." November 14, 2011. Youtube.https://www.youtube.com/watch?v=v6e6iQoYcNQ
"A Visit From Granny." The Flintstones #57. April 1970. Gold Key.
David. W. "Mr. and Mrs. J. Evil Scientist and Friends." Quasi-Interesting Paraphernalia, October 5, 2008. http://quasi-interestingparaphernaliainc.blogspot.com/2008/10/mr-and-mrs-j-evil-scientist.html.
"The Weird World of Mr. and Mrs. J. Evil Scientist" #3 (1965). Excerpts posted at I'm Learning to Share, September 20, 2008.