Adaptation Displacement: Most people remember the 1987 series. The comic book that inspired it? Not so much. This has been partially alleviated due to the advent of the internet in the 2000s, and later shows using elements more explicitly from the Mirage comics rather than the 1987 series, although the shows remain far more famous.
Adorkable: Donatello is presented as being a huge nerd, what with his love of science and engineering, but the effect is to make him charming and likable rather than a figure to mock or be creeped out by.
Alternative Character Interpretation: 1987 series: This theory seems to have arisen for some... is Irma chasing after guys really her desperation in nabbing herself a man, or, is it an act of desperation to cover up her being a closeted lesbian?
Americans Hate Tingle: Ironically, TMNT has a rather weak Japanese audience. TMNT enjoyed a few years of popularity when it was first brought there in the early 1990s, but it quickly nosedived and failed to find any continuous success due to lack of interest. The Japanese dubs of TMNT shows tend to be short lived and the Imagi movie was put straight-to-video. This is often attributed to some of the Japanese elements reaching Shallow Parody levels.
Base-Breaking Character: Venus de Milo. Most fans see her as a Replacement Scrappy for April O'Neil, but some fans think that she is an interesting concept and would like to see her return in one of the current Nickelodeon-helmed adaptations. It's particularly telling that even the franchise's creators have differing opinions on her: While Peter Laird is well-known for outright despising the character, Kevin Eastman has gone on record to say that he likes the character and hopes for her to someday make a comeback.
Better Than Canon: Some fans who do like Venus de Milo (or at least, the basic idea behind her character) tend to make her more well written, give her flaws and a different backstory.
Some works. But fans try to forget Next Mutation, and the third film.
How most fans of the 1987 series treat the Red Sky seasons (though some are fond of season eight).
Friendly Fandoms: TMNT fans and Usagi Yojimbo fans get along pretty well, thanks to the fact that the creators are friends in real life and have had their characters cross over in each others' series; Usagi has also guest-starred in every animated TMNT adaptation to date, with the exception of the 2018 series.
In 2016, a short called "Don Vs Raph" by Jhonen Vasquez involved Donnie and Raph fighting each other with trivial contests. In 2018, there was a Splatoon 2 contest themed after who the best Teenage Mutant Ninja Turtle was, with Pearl siding with Raphael and Michelangelo, and Marina with Leonardo and Donatello. The finale of the Splatfest was Raphael vs Donatello (which Donatello ended up winning).
After the Turtles hit the big time following the success of the 1987 cartoon and toys, many members of the Mirage comics' small but dedicated fanbase were turned off. The letters pages erupted with accusations that Eastman and Laird were "sellouts", circulation dipped, and sales of the adult-oriented Teenage Mutant Ninja Turtles & Other Strangeness role-playing game slowed down to a crawl. This is not really the case nowadays, since most adult fans - even those who do prefer the Mirage comics - grew up on the post-1987 merchandising empire to begin with.
Though no one was under any illusions that the Turtles weren't popular, Peter Laird's 2009 sale of the Turtles rights to Viacom shocked and alienated a number of fans, who had grown to appreciate the rare fact that such a huge and iconic media franchise was still owned by its original creator.
COWABUNGA IT ISExplanation A close-up image of Mikey's face captioned with the aforementioned phrase, used as a reaction image to scenarios where someone's about to do something exceedingly stupid, reckless, or rebellious.
Replacement Scrappy: Any version of April who is not the news reporter per the 1987 series or the live action movies is considered this to some. Except for the original April who is neither a reporter, a replacement, nor a Scrappy, making later fans view this version of the character as basically Early Installment Weirdness.
The Scrappy: Ace Duck, an early character from the toy line who was the pilot of the Turtle Blimp, is often mocked for being superfluous (why would they need a pilot when Donatello could do it and they rarely use the blimp anyway?) and for having an uninteresting design and personality. He's never had a substantial role in any adaptation, and the scant appearances he has made have always served to make fun of him- in the Adventures comics he was a Miles Gloriosus who was always shown losing to his opponents, and in the 2012 series, Shredder dismisses him as useless.
Try watching the Christmas Special, We Wish You a Turtles Christmas without laughing.
Some episodes of the 1987 series.
Special Effect Failure: Any live action Ninja Turtles production that wasn't a movie, save for the third one. "Turtle Tunes" and "We Wish You a Turtles Christmas" are the worst offenders in this regard.
Fans of the original Mirage Comics dish on the 1987 series for "selling out". Fans of the 1987 series say this about the 2003 version and its more serious tone. Fans of the first five seasons of the 2003 series will scream obscenities at Fast Forward due to its radical shift in tone, setting, and look. This was Lampshaded in Turtles Forever when the 1987 turtles and 2003 turtles arrive in the 1984 (Mirage) universe. The Mirage Turtles there call the others 'sell outs' though they eventually settle their differences.
As per tradition, the 2018 series is being blasted with this as well, most prominently for Splinter's characterization as well as Raphael being the leader at the beginning.
Usually a problem with the Turtles in Live Action Adaptations, most notably the cheap Coming Out of their Shells Tour and We Wish You A Turtles Christmas Special. Splinter often looks even worse.
The 2007 CGI movie, on the other hand, makes the turtles look quite nice, but the human models have been accused of this.
The costumes in the Operation Blue Line promotional video — which was about a light rail service that went from Los Angeles to Long Beach, and released only in California for free — blow everything else out of the water.
The original comic is a spot on pastiche of Frank Miller's work circa the early to mid 80s (mostly Rōnin and Daredevil); the writers being big fans. The best example is The Foot, who are based on Marvel's The Hand (get it?).
Also compared Daredevil's master (Stick) to the Turtle's master (Splinter). Both origins involve a truck of toxic waste too. The first issue starts with a page-by-page rip off of the toxic accident that created Daredevil, up to and including the "kid saving an old man and getting blinded" bit. If it weren't for their divergent timelines or the copyright being owned by different companies, the idea was that the blind kid is Daredevil and the canister that created him also created the Turtles. Marvel actually did have the rights to the Turtles comics at one point, but they were set in a separate universe, so perhaps the Turtles are part of the Marvel multiverse and in this one, Matt Murdock never became Daredevil and just became a blind kid.
A few elements were cribbed from X-Men as well; Leonardo was Cyclops and Raphael was Wolverine; and when Krang and Shredder◊ appear together, they seem eerily similar to Mojo and Spiral◊. While the X-Men have gone onto prominence in their own right, for a while they were less known to the public than the Turtles.
Tropes that pertain to the 1989 Nintendo Entertainment System video game:
Anticlimax Boss: After all the crap it takes to reach him, Shredder is a relative pushover due to the fact that he's the only boss in the game that can be knocked back. Players who get him in the right rhythm can just keep smacking him without giving him a chance to counter.
Breather Boss: The Big Mouser at the end of level 4. It's completely stationary, and its only attacks are occasionally firing an eye laser and dropping regular mousers. If you stand under it with Donatello and spam your upwards attack at its weak point, neither of these will ever hit you.
"Common Knowledge": The Dam stage is not the hardest part of the game; much like the infamous Turbo Tunnel from Battletoads, it's merely where the game starts getting much more difficult.
Demonic Spiders: It's bad enough that there are respawning enemies but there are some enemies that really make this game unfair and annoying to play.
The worst enemy that you will encounter in the game are the Flying Spacemen armed with laser guns in the later sections of the Technodrome. They appear and move so quickly that you almost can't react to them without getting hit. What's even worse is that there are sections of narrow halls that make getting shot or running into them an inevitability. It also takes two shots from the Scroll, the best sub-weapon in the game, to kill them. Or if you have single shurikens, it can kill them just as quickly.
The spider robots in Area 5 are notorious for making climbing sections a total pain since they move fast towards you and you're completely defenseless while climbing the wall.
The large porcupines in the underground sections of Area 5 are cheap and unpredictable as they jump and attack in completely random patterns, making it hard to not get hit by them.
By pausing the game at the right time, you can make the Giant Mouser boss fight even easier. Normally, you have to wait for it to open its mouth to attack, but pausing the game makes it vulnerable at all times.
The North American MS-DOS version has a required jump that is literally impossible to accomplish. However, you can still beat the game without cheats, if you do a sequence of extremely strange actions (although you still skip the rest of that level). If you have rope, there's a place on the overworld that you can walk, which triggers the use of the rope. Suddenly, you're using the climbing animation on the overworld. If you now enter a specific building, you will fall through the floor into a glitched level. You might end up dead, or the game asking you to insert another disk, or just trapped in a broken level, but there is a chance that the game will instead teleport you to the beginning of the next level. 
Porting Disaster: The North American PC version to say the least. The third stage cannot be completed without cheating or a very strange glitch because of a design flaw in one of the sections in the sewers. The jump is impossible to make because of the ceiling being shorter and the platform on the other side missing a block. The UK Teenage Mutant Hero Turtles corrected this by extending the platform, but retained the other design decisions that made many aspects unintentionally more difficult.
As shown by James Rolfe, the Commodore 64 version is definitely inferior to the NES version, with two of the biggest problems being the slower gameplay and that jump and attack share the same button.
The original NES game is infamous for being Nintendo Hard (its PC port is even worse), and the ones based in the most recent cartoon are underwhelming. The beat-em-ups by Konami, however, are generally considered classics of the genre, making them an aversion.
The pinball machine game is often held to be a generic, boring pinball game.
Despite hopes due to being developed by PlatinumGames, Mutants in Manhatan ended up being another case due to repetitiveness and lackluster level design.
Surprise Difficulty: Sure, the game's reputation precedes it nowadays, but back in '89 when the game dropped, at the height of Turtlemania... let's just say there were a lot of pissed-off youngsters.
The first few seconds of the intro music sounds incredibly similar to "Stone Cold Crazy" by Queen.
The Area 5 overworld theme resembles the opening riff of The Beatles' "Come Together".
That One Boss: The Technodrome boss in level 5. First of all, level 5 is That One Level in itself due to the fact that the boss is randomly placed at the end of one of three caves. As for the Technodrome itself, the prong in its front fires a powerful lightning beam that covers a third of the play area, making it nigh impossible to approach without using secondary weapons to destroy said prongnote or exploiting a glitch with the pause menu that makes the bottom half of the beam disappear. On top of that, it also has two turrets on the body firing a constant stream of bullets at you, as well as the open compartment at the top which spawns infinite Foot Soldiers to further hinder you. All of these have to be taken out if you want any chance of safely attacking the eye at the top, which is the boss's true weak point. Hope you packed a lunch!
The notorious dam level, dubbed "That Damn Dam" by some, and some fan theories persist that this level was what turned famed movie critic Roger Ebert off of video games (he played to this level, which allowed him to spot an inaccuracy in The Wizard.) The dam level owes its infamy to the following factors...
It's a Timed Mission. You are charged with defusing eight bombs under a time limit, with annoying sea life everywhere trying to inhibit your progress. Failing to defuse them all before time runs out will result in a...
Non Standard Game Over. It doesn't matter how many turtles you have left; you fail once, and it's all over. Luckily it's the only game over of its kind in this game, since according to gamers who managed to pass this level, the game gets even harder.
Then when you get to the later levels, it doesn't get any easier from here in. The third level is a maze where you have to find the correct solution to it. The fourth level, the Foot Air Base, will have you pulling your hair out. It's not only another maze, but it's also full of dangerous hazards, including liquid flame pits in some of the underground tunnels that will kill any turtle instantly on contact. Thankfully, the boss of the level itself isn't too difficult.
The Abandoned Warehouse is the fifth level and it's quite difficult due to many factors: The enemies in the caves are Demonic Spiders, and one of the three caves contains the boss, the Technodrome Defense System. If it doesn't, it brings you to an empty room, and you're forced to backtrack to the beginning of the cave. The game generates it before you enter the level, and there's no clear indication on which cave is correct until you either find an empty room or the boss. To make things worse, the enemies respawn when you exit the empty room, so you'll inevitably have at least one turtle with low health.
The final level, inside the Technodrome, definitely takes the cake. No checkpoints, an array of Demonic Spiders unique to this level, and some rooms are full of spikes. Fortunately, Shredder is an Anti-Climax Boss, and even then, he may sneak in a One-Hit Kill if you don't know the trick to defeating him, forcing you to resume from the beginning of the level.
Tier-Induced Scrappy: Really, everybody except for Donatello is low tier, and Donatello is high tier.
Donatello's attacks are slow, but have a lot of reach and do 200% damage. The only reason to play as anyone who isn't Donatello is if Don is low on health and you're trying to keep him alive, or you're playing a part of the game that doesn't involve attacking (e.g. disarming the bombs in Level 2). That being said, he's also the only character that can't normally hit low-to-the-ground enemies; he has to use a downthrust to hit them and his downthrust's horizontal range is terrible.
Leonardo is arguably the second best, but far, FAR worse than Donatello. His weapon is tied for weakest in the game, but at least it has a decent mix of range and speed.
Raphael's attack does 150% damage, and that is the only thing he has going for him. Going against him, his attack has terrible range - instead of thrusting his sai daggers forward like he should, he just sticks out his arm and spins them in place. This means it's a good chance you'll take damage while trying to damage the enemies. One could even argue that his inability to stay out of his enemies' attack range in the later levels makes him more useless than Michaelangelo, but... see below.
Michaelangelo is the worst character at all - there are not any situations in which he has utility aside from soaking up damage for the other turtles. He shares the lowest attack power in the game with Leonardo, and his nunchukus are slower and have less range than Leonardo's katanas. At least if Raphael's getting swarmed by enemies his attack speed and extra damage means he can clear his way out a little more effectively.
And You Thought It Would Fail: Many major studios such as Walt Disney Pictures, Columbia Pictures, MGM/UA, Orion Pictures, Paramount (whose parent company Viacom would ironically enough acquire the TMNT property in 2009) and Warner Bros. turned down the first film for distribution as they were worried that despite the popularity of the 1987 series and the toy line, the film would potentially be a box office disappointment like Masters of the Universe was just a couple years prior. The film finally found distribution roughly halfway through the initial production via the then small and independent production company New Line Cinema which at that point had been known more for distributing low budget B movies and arthouse fare.
Anti-Climax Boss: The Turtles finally confront Shredder in the first film and he spends roughly three minutes defeating them with little difficulty. Then Splinter appears and defeats the Shredder in one move.
The main theme for the Turtles in the first two movies.
The build-up music for the climax in the first movie.
"Message From Splinter," So awesome and bittersweet that it would be later used to pay tribute to the late James Avery in recognition of his role in the cartoon.
Complete Monster: Oroku Saki, the Shredder, is the mysterious, hateful leader of the Foot Clan, using it to satisfy his own greed and vengeful goals. Years ago murdering the object of his affections, Tang Shen, and the man she loved to sate his own jealous rage, Shredder lured dozens of troubled youths to join his Foot Clan by preying on their need for a family and turning them into criminals, all while uncaring of their well-being and subjecting them to harsh beatings as part of their daily lives. Capturing and torturing Master Splinter to gain info on the Ninja Turtles, Shredder orders the rat killed before trying to murder his surrogate turtle sons as well, claiming he will spare one of their number if the rest surrender, only to try to kill them all anyway. Returning in the sequel, Shredder forces Professor Perry to create the mutant beasts Tokka and Rahzar, threatening to execute all three of them for failure when the monsters have the minds of "stupid infants" before bragging plans to unleash Tokka and Rahzar onto Central Park and endanger countless people. When his plans are foiled, Shredder takes an innocent woman as a hostage, threatening to douse her in mutagen and monstrously transform her while he makes his escape.
Critical Dissonance: None of the films have gotten positive enough reviews to warrant a fresh rating on Rotten Tomatoes, although the first film, while not considered a work of art, has a much more positive and enjoyable reception from audiences, particularly among fans of the franchise.
First Installment Wins: The first film is the only one whose quality the fanbase can widely regard as good. The Secret of the Ooze has its defenders, but many criticize it for being Lighter and Softer and not having enough action, Teenage Mutant Ninja Turtles III is widely considered the worst film in the entire franchise, and TMNT is a Contested Sequel at its finest. To say nothing of how divisive the Bay-produced films are, although Out of The Shadows is considered a mild step-up.
Franchise Original Sin: Teenage Mutant Ninja Turtles (2014) often gets flack for making April the focus of the story, though the film still centers around the turtles. The Turtles personalities are well done, but they don't get much character development. Lacking Casey Jonesnote who was MIA in Secret of the Ooze and putting in a villain (Eric Sacks) who had nothing to do with any of the comics or cartoons prior to that point was a mitigating factor too. The thing is that this problem can be found all the way back in the 1990 original. As pointed out by CinemaSins, Raphael is the only one who gets a character arc of some sort, Leo gets some, and Donnie and Mikey don't get any at all. Plus, Danny, a minor character, had a sub-plot that while did not take over the whole film, was an odd decision. The reason why it wasn't noticeable back then was due to it being the Turtle's first film, the hype surrounding it, and a well written story with great practical effects and action scenes. The sequel, Secret of the Ooze, tried to fix the character development issue by putting the focus on Donnie's arcnote When the turtles find out they were created by accident., but it never really goes anywhere. Turtles III and TMNT (2007) both featured villains that had nothing to do with the comics or cartoons, albeit, the latter had Karai with hints of Shredder returning in a sequel that was never made. Tatsu wasn't in any prior media either, acting as a stand in for Karai, but he was the right hand man to Shredder, so that was okay. Karai was still obscure at the time unless one read the original comics, so that was understandable. Ooze had Tokka and Rahzar as expies for Bebop and Rocksteady, because Peter Laird and Kevin Eastman did not want them in the film. Teenage Mutant Ninja Turtles: Out of the Shadows, the sequel to the 2014 movie, attempted to address these complaints by putting more focus on the Turtles themselves, and also included fan-favorites Bebop and Rocksteady.
Hilarious in Hindsight: Any sports fan over the last decade who's read the stories on steroid use can now look back on Raph's comment on Casey's Jose Canseco bat with a whole new meaning.
It was a two-for-one sale.
Donatello gets ragged on by his brothers for trying to make the word "Acapella" sound cool. Years later Eminem finishes what Don started, by using that word and the meaning behind it in a crucial moment against Papa Doc in 8 Mile.
In one fight scene, Casey defeats Tatsu by swinging a golf club at him, and he promptly kisses the club, saying, "I'll never call golf a dull game again." There's a ninja game for the Atari called Ninja Golf.
Kids nowadays, watching the scene with the teens in the warehouse, may have trouble understanding what is so subversive and rebellious about using an indoor skateboarding park, playing an electric bass, spraypainting a wall clearly set up for the purpose of spraypainting, playing arcade games, and doing a little recreational gambling. Now it seems that the least horrifying thing in the '80's ("Regular, or Menthol?") is the only bad behavior in the entire scene.
Roger Ebert: I was surprised to discover it's a live-action film. I expected animation - a spinoff of the Saturday morning Turtle cartoon show. But no. These are actual human beings for the most part, including stunt men inside the life-size turtle suits (certain other characters have been created artifically by the Jim Henson folks).
Special Effect Failure: A clearly human hand swings in front of the camera as Donatello does a spin on his skateboard, there's a moment where you can clearly see a microphone cord dangling from Raphael's shell, a few instances where the head and neck seams aren't bended in properly, and a moment during Raphael's recovery where you can see the teeth of Donatello's actor Leif Tilden peeking though his mouth.
Visual Effects of Awesome: Above errors aside, the animatronic suits and puppets still look unbelievably good even today; they should, since they were created by the Jim Henson's Creature Shop and were the predecessors of all the current systems used for their full-bodied animatronics.
What an Idiot!: The two footsoldiers that tried to drown Donatello in a fishtank. The look on his face while underwater screamed "How stupid are these guys."
Woolseyism: The European Spanish dub of the film is a rather infamous example, and also overlaps with Spice Up the Subtitles as well: Unlike with what happened with the dubs of the animated series and later movies, the famous "Cowabunga!" was translated as "¡De puta madre!" (literally "That's fucking great!") at the end of the movie. The worst part of the whole thing is the fact that Master Splinter, of all people, was the one who came out with the idea of using that word. It should be noted that latter reruns of the movie in Spaniard TV gets that word censored through.