How two comic-book artists created the characters beloved by kids during the 1980s and ’90s. The original turtles weren’t so cuddly:
The original Mirage comic book really wasn’t made for youngsters. The Turtles diced up enemies while spouting the occasional curse word, and one of the Turtles’ allies was hockey mask-wearing vigilante Casey Jones, who beat down even low-level crooks with baseball bats and hockey sticks. But when Playmates Toys expressed interest in producing TMNT action figures in 1986 (we’ll get to those), the comic’s PG-13 attitude wouldn’t fit Playmates’ 4-8 year old target audience. In addition, part of Playmates’ marketing was an animated cartoon, which had to pass television censors. So to make the Turtles viable for the younger set, the Turtles had to soften up.
Among other changes, the Turtles became wise-cracking jokers obsessed with pizza, the Shredder became a typical bumbling cartoon villain, members of the Foot Clan were now robots so parents wouldn’t complain that the Turtles were too violent, and instead of ‘Damn,’ the Turtles shouted easily-marketable catchphrases like, ‘Turtle Power!’ and ‘Cowabunga!’
“The Complete History of Teenage Mutant Ninja Turtles.” — Rob Lammle, Mental Floss