Both voice actors that played Ratchet from "Ratchet and Clank" were turtles in the 2007 movie.
The second volume of Tales of the Teenage Mutant Ninja Turtles revealed what type of turtles the eponymous ninjas are: specifically, they are red-eared sliders (or Trachemys scripta elegans).
The Teenage Mutant Ninja Turtles franchise has the following tropes:
Adaptation Overdosed: In addition to the numerous animated adaptations and video games, there are also the newspaper strip, a series of British-made short comics, two anime OVAs, two live action musical specials, a couple of novels, several kid's books, magazines and crossovers and heaven know how much toys and merchandise.
Adaptation Sequence: Comic —> Cartoon —> Comic based on cartoon —> Movie —> Band —> And so on...
Exiled from Continuity: Venus de Milo was barred from ever showing up while Laird owned the franchise, due to him completely hating the character. Only in recent years is Venus showing up possible due to Nickelodeon now owning the franchise, but even now a comeback is unlikely given her rather divisive reception.
God Never Said That: Peter Laird's hatred of Venus de Milo from Ninja Turtles: The Next Mutation is quite well-known, but many fans have mistakenly believed that the franchise's other co-creator Kevin Eastman had the same opinion on Venus. According to this interview, Kevin Eastman actually likes Venus as a character and hopes for her to make a comeback someday.
Prop Recycling: Inverted and played straight for the Playmates toylines- sometimes they would reuse molds from other lines (the Muta Force exoskeletons were retooled Exosquad toys), and sometimes TMNT molds would be reused for unrelated lines (the Pizza Thrower was reused for the toyline based off Chicken Run, oddly enough).
Pet Fad Starter: Lots of kids bought pet turtles. Few were ninjas, fewer were mutants, and none lived to be teenagers.
Talking to Himself: Quite common for two characters to share a voice actor. For instance, Bebop and Rocksteady were done by Donatello and Leonardo.
Back when the Archie Comics series was selling well, there were plans to make a Spin-Off of the 1987 cartoon based on the Mighty Mutanimals, a group of allies of the Turtles in the Archie Comics. Krang was planned to be the Big Bad with the Turtles making guest appearances. A whole animation bible that featured designs for characters from the comic series and new characters created specifically for the show was submitted to Ruby-Spears, but the show quickly fell through. The cancellation of the Mutanimals animated series was what led to the team being Killed Off for Real in the Archie series at the hands of the Gang of Four.
According to an interview with Peter Laird regarding the 2014 film, Eastman and Laird were asked permission to allow the making of a live-action film featuring face-painted actors as the Turtles long before the 1987 cartoon was in development. While the film obviously never saw the light of day, Peter does wonder how things would have been if they accepted.
Creator Backlash: Although he was proud to have helped advance the art of animatronics, Jim Henson was less than pleased with the actual content of the movie. He viewed the violence as "excessive, pointless, and not his style." As such, Henson's children tried to have a dedication to his memory removed from Secret of the Ooze...which is sad and ironic considering they removed all legitimate (i.e. non-slapstick) violence from the second film BECAUSE of complaints like Henson's.
The Danza: Borderline example, Michelan Sisti wore the Michelangelo costume.
There are also numerous scenes on the farm that give the four turtles much more Character Development, expanding on April and Casey's romance, and would put later scenes into a different context:
April and Casey's reaction to Mikey's "turtle wax" joke was originally one of relief after he goes through a severe Heroic B.S.O.D. where he destroys a punching bag and part of the barn's wall
An extended training sequence where Leo proves a point by turning his mask around and fighting blind followed by the other Turtles taking turns doing the same. The scene rather famously has Donatello sporting a straw hat.
Various scenes of the Turtles training on their own or in pairs trying to master the technique Leo shows them earlier
Some of the April and Casey scenes involve him trying to help her with a stuck truck door while she declines and exits on the driver's side. Another leads into the scene of the two of them talking on the porch swing where the night before she shows him her drawings the Turtles but tries to hide the one she did of him in a beanie, they both share a laugh over it.
A game of "ninja hot potato" where the Turtles toss around an apple and the holder has to defend against the other three while taking a bite out of it. It makes the later scene where Raph finishes off an apple after defeating a squad of Foot ninjas a Call-Back.
Doing It for the Art: Why Jim Henson agreed to help on a independent film about some cartoon based on a comic book (remember, this was before big-budget adaptations of such things were common). He knew full well that to do it right he would basically have to invent new animatronic technology, and he did it so well that it became the basis of what the industry standards for animatronics are today.
Sadly, see Creator Backlash above to know what Henson felt AFTER completing his work on the movie.
Fake American: The Canadian Elias Koteas played New York's Casey Jones.
Orphaned Reference: Raphael is eating an apple after the turtles defeat the Foot's first wave during the sewer fight. This was meant to be a Call-Back to a the deleted "ninja hot potato" scene mentioned above.
Throw It In!: The reason why Raph has a Brooklyn accent in so many other adaptations is because Josh Pais (his actor in the first film) had a thick accent himself and the filmmakers decided it was just too perfect.
Originally, Steve Barron wished to replicate April O'Neil's jumpsuit look from the early Mirage comics and the cartoon. The look was going to closer resemble the cartoon with a yellow colored jumpsuit and a big head of red hair (as opposed to a green jumpsuit and brown hair). However, Judith Hoag found the jumpsuit "horrifying" and the idea was nixed. The yellow raincoat April wears in the beginning of the movie is a homage to the yellow jumpsuit she wears in the 1987 cartoon.
The scene where Raphael exits the movie theater was originally going to be different. There would have been no poster for Critters showing, and Raphael would have commented, "Cool car. Stupid costume." This would have been a reference to Batman, which was in theaters during the filming of this movie.
In the first film, Tatsu brutally beats a young Foot ninja named Shinsho due to the Foot Clan's failure. Originally, Shinsho was intended to die, but that scene was cut since it was considered too violent for some. The dialogue was replaced with the kid comforting him saying "you'll be alright," to show Tatsu only injured him.
In the junior novelization that was done of the movie, Shinsho does die. Novelizations of movies are typically based on the screenplay, so the change must have happened solely in the editing room.
In the French version of the movie, Shinsho does die.
Both the second and third movies had removed bits of dialogue explaining where Casey was during the second film. Unfortunately it seems the dialogue never went any further than "He was out of town."
Had the third movie not bombed, the fourth movie would have been about the Turtles and Splinter furthering their mutation. One of the most notable being Mikey taking a more human-like appearance, allowing him to go to the surface. In addition, a fifth turtle named Kirby would have joined the team.
With Nickelodeon owning the franchise now and producing a Continuity Reboot franchise, we likely will never see a true sequel to the 2007 film. All we have now is hints to a plot of a sequel that will probably never materialize.
The 2007 film's director, Kevin Munroe, notes that he would have loved to do a sequel exploring the Foot Clan a little more. He also states that he would also liked to have done something with the Rat King or the Triceratons.
In the 1980s, the first pitch Eastman and Laird got for a film treatment was from schlockmeister Roger Corman's New World Pictures. The idea was to have the Turtles played by four comedians who were popular at the time - Gallagher, Sam Kinison, Bobcat Goldthwait and Billy Crystal. The actors would be dressed in turtle shells and have their arms and legs painted green. Another treatment received at the time took the Turtles into R-rated territory and included a scene with partially nude nuns on roller skates fighting the heroes.