Season four of Teenage Mutant Ninja Turtles is split into two sub-sections that aired concurrently: thirteen episodes which aired daily in syndication, and twenty-six episodes that premiered in hour-long double-bills on Saturday Mornings on CBS, which would serve as its home for the remainder of the whole series. A brief "Turtle Tips" segment aired between the two episodes which served as PSA about the environment or other issues. There were a total of 20 "Turtle Tips" segments produced and aired. The syndication episodes featured the original title sequence, while the CBS episodes deubted a new title sequence, and also did away with the show's title cards. During this season, the Technodrome is back in Dimension X, having been launched through a portal at the conclusion of season three. The season premiere, "Plan 6 from Outer Space", aired in syndication, and detailed how the villains' battle fortress crash-landed on an asteroid; in the later episode, "The Dimension X Story" a volcano on the asteroid erupted, immobilizing the Technodrome by surrounding it with molten lava. "The Dimension X Story" was evidently intended to be the first episode of the CBS run, as many other episodes which aired before it from both the syndication and CBS episodes refer to the Technodrome being trapped in lava, but wound up airing very late in the season. Note that the Vacation in Europe episodes take place between the first two episodes of this season. Some episodes from this season were based off titles from other works. "Plan 6 from Outer Space" was from Plan 9 from Outer Space a 1956 film. "Four Turtles and a Baby" came from Three Men and a Baby a 1987 film. "Turtlemaniac" was from Listomania an intense fan frenzy. "Planet of the Turtles", was like Planet of the Apes but with other turtles. "Name That Toon" came from Name That Tune a game show from December 1952 to 1985 in September. "Turtles of the Jungle" had many reference to the King Kong film. "Menace Maestro, Please", Shredder dressed up like the Phantom of the Opera. "Super Hero for a Day" was from King for a Day. "Back to the Egg" was a title from a 70s song.
Dr. Polidorius creates Ray, who possesses several abilities of different marine species. He orders Ray to plant explosives everywhere in the sewers. Polidorius wants to blow them up, so the whole city will sink into the water, thus creating a new Atlantis. April O'Neil, who saw Ray during an report is kidnapped by him and mutated by Polidarius into a fish-woman who is to be Ray's mate.
However, the Turtles comes in, defeat the mad scientist, turn April back to normal and save the city. Ray escapes since he never liked working for his boss. He finds a better life under water, with the other fishes (though Ray frightens them).
- Leonardo (Cam Clarke)
- Donatello (Barry Gordon)
- Michaelangelo (Townsend Coleman)
- Raphael (Rob Paulsen)
- Splinter (Peter Renaday)
- April O'Neil (Renae Jacobs)
- Burne Thompson (Pat Fraley )
- Vernon Fenwick (Peter Renaday)
- Donald J. Lofty (Rob Paulsen)
- Dr. Polydorius (Alan Oppenheimer)
- Ray (Pat Fraley)
- Ray was initially supposed to be the character of Ray Fillet, but creator Ryan Brown, as well as Teenage Mutant Ninja Turtles Adventures writer Stephen Murphy, objected to this character being used as a villain. A fish mutant sharing the name of Ray was conceived in his stead.
- When Leonardo was finished talking to April on the Turtlecom the piece of footage of him, Donatello and Michaelangelo walking through the sewers from Raphael Knocks 'Em Dead was played, this footage was also seen later in the episode when Leonardo said "Let's fan out and search for her!" when they were scouring the sewers for April just before another piece of footage of the water flowing on the sewer floor from the same episode was seen.