Teenage Mutant Ninja Turtles II: The Secret of the Ooze is a 1991 action / family film. It was the second Teenage Mutant Ninja Turtles film, being the sequel to the 1990 film, Teenage Mutant Ninja Turtles. The Secret of the Ooze was then followed by a third film in 1993. The film is commonly abbreviated to TMNT II.

The film follows the adventures of the four Turtles; Leonardo, Donatello, Michelangelo and Raphael. Roughly resuming from the events of the last film, villain Shredder returns to take back command of the Foot Clan, and work towards getting revenge on the Turtles. When he learns the secret behind the Turtles' mutation, he becomes more dangerous than ever. The film sheds some light on the origins of Splinter and the Turtles, introduces two new villains; Tokka and Rahzar. Unlike the first film, this one rarely showed the use of their weapons. The Turtles instead fight bare-fisted for much of the film.

The film was released in March of 1991, and received mixed reviews from critics and fans. It departed from a lot of the darker feelings of the 1990 film, and in contrast was more light hearted than its predecessor. The film was still very popular, and it became the 13th highest grossing film worldwide in the year of its release.

The Turtles have been forced to move in with their friend the news reporter April O'Neil, because the Foot Clan know the whereabouts of their home in the sewers. While the Turtles are looking for a new home, they encounter a pizza delivery boy, Keno, who is trying to fight off a band of robbers. The Turtles intervene and help him. The Foot Clan is no longer as large as it was in the first film. Master Tatsu, Shredder's right hand man, attempts to take control of the gang but is challenged by Shredder himself. Shredder was thought to be dead, falling from a rooftop into a garbage truck's trash compactor after a short battle with Splinter at the end of the first film. He now appears physically deformed obsessed with obtaining revenge. He sends a Foot member to pose as an intern at the news network and trail April.

April is doing a report on a company known as TGRI. A scientist employed by the company discovers that toxic waste produced by the company has caused mutation in nearby flora, producing exponential growth. The Foot member posing as an intern informs Shredder of this, whereupon Shredder proceeds to dispatch the Foot Clan to obtain some of the waste. Splinter sees the report on television and later shows the Turtles and April the ooze canister that had caused the Turtles mutate in the first place. Splinter pieces the broken canister back together, revealing that it was from the TGRI company. The Turtles infiltrate the TGRI offices to get the ooze, only to meet Tatsu and the Foot.

Despite the Turtles doing their best to stop them, Tatsu and the Foot escape, taking the last canister of ooze and head TGRI scientist Professor Jordan Perry. Shredder instructs Perry to use the ooze to transform a snapping turtle and a wolf into monsters, creating the characters Tokka and Rahzar. Perry does this, but alters the ooze to decrease the intelligence of the mutants, making them infantile in intellect. When Shredder tells them to call him "Master", they misinterpret this and call him "Mama" instead, enraging him. He initially orders Tatsu to kill them both; when he sees a demonstration of their immense strength, he decides to use them as weapons. He releases them into city streets, where they amuse themselves by breaking every object they can hold, including lamp-posts, mailboxes, and cars.

Raphael goes alone to pursue the Foot while the other three Turtles find a new lair in an abandoned subway station. With the assistance of Keno, the Foot headquarters is infiltrated, but Raphael is eventually captured by Shredder. Keno is able to inform the others, who go to save Raphael. After rescuing Raphael and Professor Perry, being themselves aided by Splinter, the Turtles are vanquished in battle by Tokka and Rahzar. Professor Perry and the Turtles develop an antidote to the ooze's effects. After creating a successful formula, they trick their enemies into eating it by hiding it in doughnuts and appealing to Tokka and Rahzar's hunger. Tokka and Rahzar eat some, but soon discover the antidote and are stimulated to generate fury.

The Turtles find themselves confronting the Shredder's mutants at a nightclub, in full view of every guest and performer. To appease the initial panic, Vanilla Ice, the lead singer at the club, improvises a rap song whose refrain is "Go Ninja, Go Ninja, Go!", which is then sung as background music to the fights taking place in the club. The Turtles use fire extinguishers to stimulate a swift activation of the antidote by spraying carbon dioxide into their enemies' throats. The mutation is reversed, reducing the two monsters to their natural forms. The Shredder menaces the club, breaking the nearly carnival-like emotional backdrop created by the song. The Turtles use a sound amplifier to magnify a single noise produced by an electric guitar, resulting in a powerful sound-wave that throws the Shredder out of the club and into the area among the docks below.

However, Shredder uses a vial of ooze to become a superior form of himself, extemporaneously called Super-Shredder. While fighting underneath a pier, the Super-Shredder, desperate to destroy the Turtles and heedless of all else, wrecks the structure, bringing it down on himself. The Turtles escape thanks to their reptilian nature. Shredder's hand emerges from the wreckage, but moments later falls down, indicating that he has died.

The Turtles return to their new lair, where Splinter asks whether they were seen. They deny it, until Splinter displays a newspaper having a front-page picture of them, taken at the nightclub where they fought Tokka and Rahzar. It is not explained how the newspaper's publishers managed to print the story between the time of the fight and the Turtles' arrival home, nor how Splinter managed to get a copy. Splinter advises them to practice harder, then orders them to perform ten flips each, reminding them "Go Ninja, Go Ninja, Go!" The screen freezes as they begin the first flip, whereupon Splinter shouts "I made another funny, ha ha ha ha!"

Mark Caso as Leonardo: Leonardo is generally considered the leader of the Turtles within the TMNT franchise. He wears a blue bandana and carries two katanas on the back of his shell. He is voiced by Brian Tochi.

Michelan Sisti as Michelangelo: Michaelangelo is one of the four Turtles, and is the most light-hearted of the four in both the film and the TMNT universe. He wears an orange bandana and carries dual nunchaku on each side within his belt. He is voiced by Robbie Rist.

Leif Tilden as Donatello: Donatello is one of the four turtles and is known for his technological expertise within the TMNT franchise. He wears a purple bandana and carries a bo on the back of his shell. He is voiced by Adam Carl, who replaced Corey Feldman in this film only.

Kenn Scott as Raphael: Raphael is the more aggressive and rebellious of the four turtles. He wears a red bandana and carries two sai in his belt. He is voiced by Laurie Faso.

Paige Turco as April O'Neil: O'Neil is a news reporter, and the human companion of the Turtles and Splinter. Paige Turco replaced Judith Hoag for the remainder of the series.

David Warner as Professor Jordan Perry: The professor works for the TGRI company as head scientist. He works with the Turtles to create an antidote for the mutated Tokka and Rahzar.

Kevin Clash as Splinter: Splinter is the master and father figure of the turtles, and is a mutant rat.

Ernie Reyes, Jr. as Keno: He is a pizza delivery boy who meets the turtles in the beginning of the film and befriends them.

François Chau as Shredder: Shredder is the main villain in the TMNT franchise. He survived the battle with Splinter from the first film, and wishes to get revenge on Splinter and the Turtles. François Chau replaced James Saito in this film; He is voiced by David McCharen.

Toshishiro Obata as Tatsu: Master Tatsu is Shredder's right-hand man and temporary leader of the Foot Clan in Shredder's absence. He is voiced by Michael McConnohie.

Mark Ginther as Rahzar: Rahzar is a mutated wolf created by Shredder using a canister of ooze from the TGRI company. He is voiced by Frank Welker.

Kurt Bryant as Tokka: Tokka is a mutated alligator snapping turtle also created by Shredder using the canister of ooze from TGRI. He is voiced by Frank Welker.

Kevin Nash as Super Shredder: Shredder becomes Super Shredder as a result of using the ooze which has mutant effect, making Shredder a superior version of himself.

The film was released less than a year after the first, using the taglines "Back by bodacious demand" and "Cowabunga, it's the new turtle movie". Teenage Mutant Ninja Turtles II: The Secret of the Ooze was released in theatres on March 22, 1991 in the United States, and was subsequently released in numerous countries from June through to August. The film has a 20% freshness rating on Rotten Tomatoes, which collates film reviews, but has a 76% freshness from users. The film opened at number one in North America on its first weekend of release, taking in over $20 million (USD), eventually making $78,656,813 in total. The film was a success at the box office, but made less than the first film. Some fans noted that½ there was also a reduction in the use of weapons by the turtles in the film, perhaps due to violence in the first film. (Leonardo and Raphael only use their weapons once each in the movie, for example.)

Due to the large success of the first film, it was generally expected that a sequel would follow. The film was produced on a budget of $25 million (USD), higher than the budget of the 1990 film, which was $13.5 million. Like the first film, New Line Cinema distributed The Secret of the Ooze. Both the voices of Michaelangelo and Leonardo reprised their roles in the second film, whereas Corey Feldman did not voice Donatello in the second movie. A different actress also played April O'Neil, with Paige Turco playing the role, instead of Judith Hoag. The character of Casey Jones who was a prominent character in the first, did not have a part in film. Ernie Reyes Jr. who was Donatello's fight double in the first film, was cast as a new character; Keno, as producers liked Reyes so much they created the role just for him. Todd W. Langen returned from the first film to write the screenplay.

The abandoned subway station, which serves as the new lair for the Turtles, is based on real-world abandoned New York subway City Hall Station, of the former Interborough Rapid Transit company. During filming of the scene where the Turtles are trapped in the net and fall to the ground, one of the stuntmen broke an ankle. Some filming took place in North Carolina, much like the first, where the New York City skyline was created at the North Carolina Film Studios. The building used for the entrance to April's apartment is the office to the New York location of Jim Henson's Creature Shop, which did the animatronics work for the film. The film is dedicated to the memory of Jim Henson.The dedication appears at the very beginning of the film.

The Teenage Mutant Ninja Turtles franchise was arguably at the height of its popularity around the time that The Secret of the Ooze was released in theatres. A number of tie-ins were brought out alongside the release of the film. A new line of toys were introduced for the release of the film, including "Movie Star" toys of all four turtles, with the box art depicting stills from the film, as well as a cartoon rendition of the turtles gathered around a canister of ooze in the top right corner of the package. In contrast to the usual Turtles' figures, the film series figures were softer and more rubbery, to better reflect the look of the animatronic costumes used in the films. They also featured ball joints at the neck, shoulders, and hips, and each figure came with a small, translucent canister of Ooze. An official film adaption was also released by Eastman and Laird.

Figurines of Super Shredder, Tokka and Rahzar were also available, though they were not as closely aligned to the film as the four turtles were. The Playmates company produced the figurines. The Turtles franchise had by now also immersed itself into the food industry, with characters from the franchise appearing on numerous food products. Royal Gelatin Desserts adapted the "Ooze" name into their product, and featured the Turtles on the packages. The boxes included various recipes involving ooze in some form.

An original motion picture soundtrack was released alongside the film in 1991 by SBK Records.

The soundtrack featured 10 tracks from the film. The soundtrack featured music from artists such as Ya Kid K, Cathy Dennis and David Morales, Tribal House and Dan Hartman. However, the most famous song featured on the soundtrack was Ninja Rap by rapper Vanilla Ice.

The song featured strongly within the feature film, as Ice makes an appearance as himself, and begins to freestyle a ninja rap song when the turtles end up fighting Tokka and Rahzor within the club where he was performing. A music video was also produced for Ninja Rap at the time of the film's release. The soundtrack also features two original pieces from the Orchestra On The Half Shell. The original music was done by John Du Prez, who won a BMI Film Music Award for his work.

The film has been released on DVD, though a special edition has not yet been made. Teenage Mutant Ninja Turtles II: The Secret of the Ooze is also available in a three-set package with the other two films that were made in the 1990s. However, at present there is no special edition release of the film, with the DVD release being restricted to basic features such as the theatrical trailer. Alternate versions of the film have existed on home video that have differed from the original theatrical release. The opening fight scene was shortened for the home video release, and in the United Kingdom in the older releases, the film was heavily edited to remove the scenes involving nunchakus. In the DVD release, while Michaelangelo is being swung around by Rahzar, the line "Help, Leo!" is cut.