In the original comics, all four turtles had red bandanas. For the TV show, they were each given a different color to make it easier to tell them apart: Leonardo has a blue bandana, Raphael a red bandana, Donatello a purple bandana and Michelangelo an orange bandana. This color scheme became so popular it eventually became a staple of the TMNT saga.
The Turtle's rival group of ninjas, "The Foot", are a tongue-in-cheek reference to the extremely popular "Wolverine" comic by Frank Miller and Chris Claremont; in that series, which had just been published when the Ninja Turtles first appeared, Wolverine was constantly dealing with a group of ninjas called "The Hand".
Begining in Season 4, the show started phasing away Michaelangelo's nunchucks and began having him use the Turtle Line, a turtle shell shaped grappling hook used by all the turtles, as his main weapon. Starting in Season 5, the nunchucks were not even kept on Michelangelo's belt and disappeared without any explanation. This is a direct result of nunchucks being outlawed in many countries and these countries had to edit out any footage of Michelangelo using his nunchucks. Since the show went international, MWS changed it for everyone.
The mutagen ooze was depicted slightly differently in this cartoon; rather than causing its victims to increase in size, it caused them to transform into a hybrid of their original species and whatever creature they have most recently been in contact with. The mutagen ooze also had many color variations through the series, the mutagen seen in Season 1 that mutated the turtles, splinter, and Bebop and Rocksteady had a pinkish glowing color. However starting in Season 3 green mutagen was introduced, which became the most common color in the series. It recanted, and even shown in the 2nd intro sequence, that the mutagen that mutated the turtles was green. Later a rainbow variant of the green mutagen was shown.
In the original Mirage comic books, the Foot Soldiers are real people, not robots. As such, the comics showed the turtles killing Foot Soldiers in fight scenes. Due to issues of violence in children programs, the soldiers were changed to robots and the turtles are never seen killing anyone despite their use of offensive weapons.
The producers tried to get the voice actors to be a little more serious in their performance since comic book on which the series is based was serious. But the voice actors would have so much fun recording together that they played up the comedic aspects of their characters. Also, most of the voice cast had young children and they wanted them to be able to enjoy the show.
When production started for CBS the show was aired on an hour block on CBS Kid TV. The first episode consisted of an action-oriented episode and the second episode was more comedic and highlighted one of the four turtles. The latter was type of episode was discontinued in Season 6 when the show went to just one episode per week.
For Season 4, 28 episodes were produced for syndication and 26 episodes were produced for CBS' "Kid TV" Saturday morning line up. However, 15 of the syndicated episodes never aired in 1990. The "European Vacation" episodes were not seen in the United States until USA Network started showing reruns in late 1993, and The Easter themed episodes, "The Turtles and The Hare" and "Once Upon A Time Machine" weren't seen until 1991. An easy way to tell that these are Season 4 episodes is: the original intro is used, title cards are used, Michelangelo uses his nunchucks, and the Technodrome is stuck on an asteroid in Dimension X. These episodes were delayed because of animation and schedule problems.
When the show aired on CBS, many Public Service Announcements aired on CBS Saturday Morning line up. These PSA's were called "Turtle Tips" and intended to benefit the public interest, by raising awareness of environmental issues.
Like other cartoon series built around an action premise, TMNT did not escape criticism by parent groups for its violence. In the case of this series, schools began reporting that children began getting into fights during recess and seriously hurting one another in an attempt to mimic the martial arts moves depicted in the show.
The Turtles were originally hired to write the theme song but they never got around to it. Chuck Lorre and Dennis C. Brown wrote the original theme song in two days and Jim Mandell provided the lead vocals.
CBS decided they wanted the show to be darker after getting beat in the ratings by X-Men (1992), a show featuring the original comic book mutants. Starting in Season 8 the show became darker and more serious, a tone that was a closer match to the original comic books the show was based on.
Because of heavy censorship in the United Kingdom, the original intro sequence was heavily edited replacing the word "ninja" with "hero" or "fighting", using a digitally faded logo instead of the animated blob, and removing any scenes in which Michelangelo wields his nunchucks, replacing them with random clips from the show. When the show started airing on CBS, a new more international friendly intro sequence that was produced. The 2nd intro still referenced ninjas, but didn't feature Michelangelo wielding his nunchucks. They were just stored on his belt like in most Season 4 episodes.
In the comics, movies and other ninja turtles TV shows, the turtles are often referred to as abbreviated versions of their names Leonardo-Leo Raphael-Raph Donatello- Donny Michelangelo- Mikey. In this series, they are always referred to in full context.
Lotus Blossom bares a resemblance to Karai from the original comics. Which lead fans to believe that she is an alternate animated counterpart to Karai. Despite popular belief Lotus actually first appeared on the show three years before Karai was introduced in the comics.
All of the voice actors performed their roles together in the same room. This was so important to Fred Wolf that he told the voice actors that the recording session took priority and if someone couldn't make it to the recording session, they would be temporarily be replaced. This is why some of the characters had alternative voice actors, who temporarily took on the role when the original was unavailable.
Writer David Wise admitted that he preferred and always wanted the show to have the serious action oriented tone of the last 3 seasons. He pointed out that Season 1 had a perfect balance of real drama and humor and that Season 2 is when the show started going in a more humor driven direction. However, he did not enjoy working on the final 2 seasons because of network meddling.