These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Ch'rell was an Utrom criminal who was imprisoned by his people for his various crimes. Ch'rell managed to force the transport ship he was being carried on to crash on Earth. Ch'rell escaped and took the guise of an Japanese crime boss named Oroku Saki, better known as the Shredder. Shredder wanted revenge on his people and went to great lengths to find the Utroms still on marooned Earth.
In Teenage Mutant Ninja Turtles 2003 Shredder attacked Splinter's master, Hamato Yoshi, believing he worked for the Utroms. After having his minions work over Yoshi with torture, Shredder personally killed Yoshi, an act that would lead to Shredder becoming the Turtles Arch-Enemy. Shredder's Foot Ninja also kidnapped innocent people and mutated them into monsters to use as slave labor to try a locate a possible Utrom base underground. Shredder has shown to be a very cruel boss. He murders one of his men who failed to deliver some stolen goods for him, due to the Turtles involvement. Shredder also would punish Baxter Stockman for his failures, by grievously injuring him, until eventually Stockman was nothing more then a Brain in a Jar. Shredder also displayed a complete disregard for human life, after an Triceraton Invasion resulted in Beijing becoming a city floating in the sky, Shredder decides to steal the anti gravity generator that is keeping the city in the air. When Karaiobjects noting that stealing the generator will result in the city crashing into the ground and killing millions in the process, Shredder overrules her and tells her to do it anyway. Some of Shredder's worst crime happen when Donatello visits a Bad Future where Shredder is a dictator who controls the world. Shredder has Secret Police on the streets to round up any dissenters and is using both Utrom and human slave labor (with humans having to work 18 hours a day) to build a giant teleportation device, so Shredder can conquer other planets. In this future, Shredder executes his former servant Hun, while Hun is begging to be let back into the Shredder's service.
Canon Sue: Probably one of the reasons Cody Jones is considered The Scrappy in most fans' eyes. Every other episode he seems to be saving the Turtles from some bad situation, despite the fact that they've been learning the ways of ninjitsu their whole lives, whilst he's only been learning ninjitsu for the past few months...
Crack Is Cheaper: Ever since Nickelodeon bought the franchise, they're more or less swept the 2003 cartoon under the rug. The DVD volumes and sets previously released by 4Kids have gone out of print, and good luck trying to get them all up to the Fast Forward season now: several of them go anywhere from $75 up to $200.
Deader Than Disco: The show is nowadays considered this, much to the immense chagrin of its respective fans, even though it was pretty popular its heyday to either children who were exposed to this version first and never heard of the 1987 cartoon or any other incarnation or old-school fans who liked the extension of a beloved show from their youth reworked in an different light (or to anyone who was a fan of the original comic book seeing an animated series more faithful to the franchise's original content). This was for the most part caused by the basebreakingFast Forward and Back to the Sewers seasons and the Turtles Forever movie, which many view as openly mocking the original animated series (and, by extension, their fans), the obscurity/expense of the show's DVDs and the fact that 4Kids have since lost the TMNT rights to Nickelodeon, who by and large refuses to even acknowledge this version as existing. During the Christmas 2014 season, many were shocked when Nicktoons actually played a couple episodes of this version during the Turtles Throwback marathon, but it's still unlikely one will be seeing any of the 2003 Turtles merchandise in stores again, and even so, chances are it won't be in the same volume as the otherversions.
Fridge Brilliance: After his defeat in "The Shredder Strikes, Part 2," Shredder makes it a point of going after the Turtles and eliminating them. Seems like common sense and simple revenge, right? But then "Timing is Everything" showed Shredder after his first defeat facing the more-skilled Turtles by way of time travel. He knew they would become more powerful and eventually defeat him (as Raph says), so his motives weren't pure revenge.
Fridge Horror: Possibly mixed with Harsher in Hindsight. An un-produced episode of the Ninja Tribunal season was going to reveal that Hun and The Garbageman were conjoined twins separated at birth by a back-alley surgeon. That was horrific enough that it got the episode scraped by the network, but it gets even worse when who realize that it was hinted at two seasons earlier during "Same As It Never Was." Brings the Shredder's punishment of Hun and Stockman to an all-new level of "apropos."
In "The Shredder Strikes Back, Part 2" many of the Foot Ninjas are knocked out by the Turtles and Master Splinter, so when the Shredder blows up the shop (and by extension, the apartment above), it can be assumed that they perished in the resulting explosion. Although Stockman says in "Tales of Leo" that 'there's no conclusive proof to say anyone, turtle or human, perished in the fire', that still doesn't mean that all of the Foot Ninjas escaped the blast; it merely means that Stockman doesn't have enough data to prove it
In "Exodus", it was promised "One of these characters will never be seen again.", and after the episode, Ch'rell is banished to an ice planet, likely never to be seen again... That is, until Turtles Forever, but even before that, Peter Laird confirmed that the Triceraton Shredder shown in concept art of a possible second Fast Forward season would have been Ch'rell hijacking the body of a Triceraton soldier, and Back To The Sewers not-so-subtly implied in its first episode that Ch'rell would fight the other two Shredders in the show (there would have been an arc called "The Shredder Wars"). Making the claim that Ch'rell would never be seen again hysterical.
On a similar note, there's this exchange, from season 5, before the Cyber Shredder was introduced (and, consequentially, before Turtles Forever and the whole 'Multiverse' thing).
Early on in season 1— the episode "The Garbageman"— Mikey tries out several catchphrases, much to his brothers' distaste. One of those catchphrases is "It's trench-coat wearing time!". Nobody (except the fans) seems to have a problem with "It's ninja time" five seasons later.
The Dark Turtles of the Fast Forward season have far more distinct designs than the Turtles, with Dark Leonardo having the most balanced physique, Dark Raphael having a bulkier form, Dark Donatello being taller and slimmer, and Dark Michelangelo being somewhat smaller than the rest. Barring Michelangelo, almost all of the design traits are exactly like the next incarnation's Turtles, who were all made distinct aesthetic-wise. Dark Raphael also has spikes protruding from his body and shell, which also makes him resemble Raphael's mutated pet Turtle Spike, who would become the next incarnation of Slash.
Magnificent Bastards: The Ninja Tribunal. Can also be considered Guile Heroes since they are on the Turtles' side. Plus, the fact that they plan for the turtles to meet their destinies whether they are able to defeat the Demon Shredder or not is considered GOOD magnificent bastardom indeed.
The Heralds of the Shredder, a.k.a. the Foot Mystics, count as well for two of their successful plans; one to have Bishop free them by destroying the Heart of Tengu that allowed its user to control them, and the next one to resurrect their true master, the Demon Shredder, despite the failures of their demonic mooks.
Moral Event Horizon: For the Shredder, this was the episode "Mission of Gravity", where we learned that not only is he willing to kill millions when it serves his purposes, he'd also do so when it wouldn't.
Nightmare Fuel: Baxter Stockman, especially the episode "Insane In The Membrane".
Shredder's reaction to Stockman's continued failures.
Same As It Never Was, the episode seemed to have been intentionally designed to be utterly terrifying, and probably to show exactly what the Shredder would do if he were to take over a planet, the results are, yet again, terrifying.
The Shredder trapping the Turtles, Splinter, Casey, and April in April's antique shop closet by setting the place on fire using the gas pipes. It set up a big two-part episode cliff-hanger for the show, which no doubt scared a lot of kids back in the day.
The Scrappy: Stockman is hated for repeatedly cheating death. Also for being flat out arrogant, seeing the mutants in the show as "stupid animals", even though 2 of those stupid animals (Donatello and Leatherhead) are more intelligent than him and just acting condescending to anyone he deems to be intellectually inferior.
Starlee's family is rather annoying. Her mother is snobby and thinks of her species and planet as above others and acts rather rudely (she thinks Donatello is a criminal for wearing a mask, and asks if he's had his vaccination shots when he knocks everyone down to avoid getting hit by a laser). Her little brother, also messes with things he's not supposed to touch and gets away with it apart from Starlee yelling at him. It's not much of a surprise to see why Starlee didn't want everyone to meet her family.
Seasonal Rot: By Fast Forward, although some people would place it even earlier.
Really Season 4 was the high point with some complex and surprisingly well written arcs for both Leonardo and Michelangelo. The two retools made the show much more child friendly and typical (robots, digital realms, collect the clues saga), but Season 4 stands as a nice end to a good cartoon.
A few fans stopped watching the show when it was revealed that the Shredder was an Utrom.
Season 5 is a Base Breaker: many people felt it did a good job wrapping up the remaining plot threads from the previous season, while others felt it was overly gimmicky and too much of an anime/Avatar ripoff, abandoning the series' original roots of being influenced primarily by the original Mirage comics.
Strawman Has a Point: Throughtout Season 4, Leonardo becomes increasingly hardened and more of a jerk than Raphael ever was. After the Turtles and Casey fail to stop a Purple Dragon convoy in "Dragons Rising," the trope is invoked as Leonardo delivers a pretty brutal "The Reason You Suck" Speech:
Leonardo: Half! We stopped half and only because we got lucky! Is that good enough for you? Is it?! We're always one step behind! We act like a bunch of amateurs! How many times are we gonna get beaten before you guys wise up and realize this isn't a game?! (storms off) Raphael: I hate to admit it, but he ain't wrong.
Tear Jerker: A few episodes. Especially any episodes involving Nano.
Kirby giving Donatello a sketch of him with a ray gun and final words: Don - "Life at best is bitter sweet." Take care of yourself. - Kirby
The entire 2003 series got accused of this by fans of the '80s cartoon, with complaints that they wished it was more like the "original" series. The irony being that the 2003 series, was far more faithful to the REAL original Turtles of the comics, than the '80s series ever was. It was hit with this even more in Japan, where they were more fond of the 1987 Turtles.
Some fans of the old cartoon were fine with the 2003 cartoon at least existing, until Turtles Forever came out, which seemed to some to go out of it's way to mock the 1987 series and make the 2003 series look superior.
Shredder being an Utrom. Good god, people raged at that back in the day.
Of the many complaints Back to the Sewers had, one of the biggest was the change in art style compared to the first six seasons.
They Wasted a Perfectly Good Character: Or characters, in this case The Dark Turtles. Mostly due to their subplot being dropped to make way for Back to the Sewer. Dark Leo's time with the turtles in their final appearance suggested the four had a chance to turn good at some point, but this would never come to pass.
Values Dissonance: Jammerhead refers to the Turtles in "Playtime's Over" as "buggers" - whilst this is no more offensive than 'jerks' or 'boneheads' in America, in the UK this is quite a rude word, and not one you'd expect to hear in a children's show.
Villain Decay: Inverted, the Shredder managed to stay a dangerous antagonist, he even managed to top himself in every evil plan he committed, with the Utrom Shredder being considered the most dangerous of the bunch.
Hun himself though, seems to play it mostly straight, while he can fight the Turtles, he gets significantly more pathetic, while later seasons do try to avoid it, he ends up becoming a bigger loser, though, to be fair, in Back To The Sewers, he learned more techniques that allow him to fight the Turtles and even becomes a Crime lord... Doesn't stop them from learning to fight him again, although in Turtles Forever, he turns into a Turtle Monster, he ends up being so powerful that the Turtles can't lay a scratch on him.
Karai suffers this badly in season 4. From one appearance to the next, she goes from destroying the turtle's lair, all of their vehicles, and nearly killing 3 out 4 turtles and Splinter to playing and losing a rather humiliating game of keep away for a McGuffin against Leo and Mikey, including a sequence where they pick her up and drag her by the legs before throwing her out of an elevator shaft, in a manner more suiting Bebob and Rocksteady.
The Cyber Shredder, granted, it's the Shredder's data before Shredder became more and more Genre Savvy, but... His plans constantly fail and get repetitive, even when he does get out of Cyberspace.
Villain Sue: Bishop, due to the sheer ease that he manages to outfight the Turtles, Hun & Karai, his repeated elaborate escapes & the fact that even when he loses, he still wins in the grand scheme of things.
To recap, in Nano's first appearance, it's defeated by getting dropped into a vat of molten steel, and survived, and only to get broken into pieces when returned. An AI that's only a child at heart and doesn't fully understand right from wrong gets defeats more painful that what the villains in the series endure.
Nano's father figure Harry the Pick-Pocket is also a little bit sympathetic. True, he mainly went along with Nano's delusions that he was its father so it could help him in his crimes, but at times he acted as if he actually cared about Nano. This is made especially apparent when he mourned Nano's demise in its debut episode and was overjoyed to see it alive and well in its second appearance.
Doctor Stockman is an unusual example of a Woobie. A fairly standard villain, it is only once we get to ‘Insane in the Membrane’ that the audience learns anything about Stockman’s backstory, with the flashbacks to his childhood revealing the trauma he went through as his mother died from an unknown illness. In addition, he is slowly mutilated by the Shredder throughout the course of the first couple of seasons, and whilst this typically elicits little sympathy from the audience due to his thoroughly vile personality, when he is brought back once again by Bishop in ‘Adventures in Turtle Sitting’, we discover just how much he wishes to be free of his horrible existence.
Stockman: Why couldn’t you finally let me rest in peace? WHY?
Donatello has had to deal with some of the worst experiences over the course of the show. He's been in a Lotus-Eater Machine where he's seen Angel die before his eyes, been transported to a Bad Future, where he sees all of his brothers die before his eyes, and learns that Master Splinter and Casey Jones are already dead, been captured and Mind Raped by the Triceratons, and been infected by a mutant virus that turned him into a mindless savage beast and nearly killed him. All of this to the most peaceable, kindly turtle of the team.
Though not popular, Serling is probably one of the biggest woobies. Most, if not all the fans hate him and in-universe, the other characters treat him like a slave sans Splinter and Cody, suffers bad luck which is sometimes caused by his buttmonkey status, while other times, his pain and suffering is deliberately caused by the turtles (i.e. trapping him inside a video game surronded by extra lives that look and act like the turtles). Honestly, it's a miracle he never tried to commit robot suicide.
The sheer fact that the writers seem to cause Leonardo the most emotional and physical pain out of any of the protagonists makes him a Woobie in the eyes of some fans. Throughout the course of the entire show he's typically the most likely to suffer a No-Holds-Barred Beatdown, teeter on the brink of death, experience Heroic BSOD and is even acknowledged in one episode by Michelangelo to shoulder the majority of the responsibility so that his brothers are free to be themselves. What's more, his near decline into Knight Templar-hood in Season 4 as he struggled to deal with Post Traumatic Stress Disorder left many fans yearning to just wrap him in a blanket and give him a big hug.
Poor Leatherhead! He's been flushed down the toilet when he was barely more than a hatchling, rescued and reared by the Utroms, only to be left behind all alone when they returned to their own world, manipulated and lied to by Baxter Stockman, buried beneath a pile of rubble, tortured by Agent Bishop, which has left him with parts of his personality he must work hard to control, pursued by a crazed hunter, believed he'd badly hurt/killed Michelangelo in a fit of rage. Don't worry: Mickey was fine, which left him consumed with grief and believing he was nothing more than a monster and worthy of death, and finally his good friend Donatello was infected by Bishop's mutant virus and turned into a mindless monster. Leatherhead did eventually help Stockman to develop a cure for the virus in time to save Donny, but he was obviously deeply upset to see Donatello that way, and to be initially unable to help him. He may be one of the biggest and strongest heroes in the show, but it seems like just about every time he appears he's suffering from some kind of mental or physical anguish.
The Fugitoid/Professor Honeycutt: really depends on whether you find his personality + voice annoying or endearing.
One time character T9581. He started life as a human, got married and had a child, only to be mutated by Bishop into a hideous monster with apparently no way of communicating his feelings or intentions, was locked away in cryogenic stasis only to be freed by the Purple Dragons, who started to attack him, escaped from them only to be attacked by Leo and Casey who mistook him as dangerous, and then was attacked by Bishop and seemingly blown up. Although he escapes, he has no way of returning to his former life or family, and the last shot we see of him is the poor creature clinging to a buoy, gazing sadly at the gazebo where he got married. His whole story is a really tragic Tear Jerker.