California Doubling: The series was filmed and set in California, while the movie was filmed in Queensland, New South Wales and the Northern Territory in Australia. The movie actually looks rather good for its budget, and some industry analysts have suggested it helped promote the use of Australia as a cheap filming location.
Richard Genelle (Ernie) was actually present for the entire two months of filming and was supposed to appear in his new place for the movie, called Ernie's Waterside Cafe. The Waterside Cafe was meant to substitute for the Angel Grove Gym and Juice Bar and is only seen in the film when all of the Ooze-possessed kids, as well as Bulk and Skull, are found and recruited by the new kid character Fred Kelman. The Rangers were originally meant to arrive there at the end of the rollerblading sequence. This scene was intended to introduce Fred, with Bulk and Skull also being present.
Deleted Scene: At conventions, the film's actors have commented on various scenes filmed that didn't make it into the movie, such as the Rangers doing some preliminary training between being given the ninja robes by Dulcea and traversing into the forest. In particular, Tommy's was apparently seen practicing some superhuman kicks similar to the corkscrew kick he used to finish off the last gargoyle.
The first sequence inside the Command Center included exposition about the "Order of Medelan" that originally imprisoned Ivan Ooze, and had Zordon giving the Rangers new "Opt-Scan" devices for their helmets, one of which Rocky later uses in the construction site.
Upon arriving on the planet Phaedos, the Rangers were to follow Dulcea into her home inside a temple, where she would teach them the ways of Ninjetti. This was cut after her character's last-minute double-recasting.
A scene of the Rangers resting inside Dulcea's compound, replete with colour-coordinated beds, where she would give exposition on her backstory and her connections to Ooze and Zordon was cut.
A number of scenes set in Angel Grove, showing Ivan's gradual takeover and brainwashing of both the adult and child population through his alter-ego as the Wizard. Many of these scenes also featured Bulk and Skull, who were reluctantly recruited by Ooze to work in the chemical plant.
Extended scenes of Ooze's robots rampaging through the streets.
A longer sequence of the kids wrecking the Waterside Cafe at Ooze's insistence.
The extended climax was heavily trimmed due to a mix of time and budgetary issues:
Fred originally sprayed the kids at the Cafe with a firehouse to break them out of their brainwashing, explaining how he knows to use it against the adults. This was changed to him simply whistling and getting their attention.
Fred had a longer speech pleading the kids to fight back against Ooze, but it was cut due to the director being unsatisfied with the actor's performance.
Ooze was meant to stand atop the tower and shoot lightning from his hands, creating an army of monsters below. This scene was shot but cut after the director's was unsatisfied with the depth of the image, due to the backdrop being smaller than anticipated.
An extended fight between Goldar and Ooze atop the tower.
The first fight scene in the construction site involved the Rangers fighting mutant, humanoid rats. However, it was universally agreed upon that the rats looked absolutely horrible, and they were replaced with the Oozemen. The rats later showed up in the TV series, in Season 2's "Return of the Green Ranger."
The Tengus were used in the third season as the Tengas.
Much later, one of the stone gargoyle-guardians the Ninjetti Rangers fight appeared in the background of an episode of Power Rangers S.P.D..
The Other Darrin: Zedd, Rita, Goldar, and Alpha are portrayed by different suit actors, though, thanks to their voice already being redubbed, they sound just the same as they did on the show (though Zedd sounds a bit deeper than his show incarnation). Their suits are slightly modified as well, to go with the Darker and Edgier feel. While Rita remains the same as she usually is, the "Z" on Zedd's forehead crest is notably lower down, he gains platinum pauldrons, and the gaps in his helmet's mouth are more closed up. His brain is also visibly pulsating. Goldar is inbetween the two: while he retains overall the same look, his face is more feline than monkey-like, and for some odd reason he doesn't carry his sword on him.
Goldar looking more feline-like makes sense when you consider that his original suit's face is supposed to be leonine, as his Zyuranger self is based on a griffon.
Zordon is played by Nicholas Bell here; when he plays the character as he's dying, that's his real voice.
The Other Marty: Gabrielle Fitzpatrick was the original choice for Dulcea, but had to back out to remove a cyst. Mariska Hargitay (yes, that one) was brought in as her replacement. Filming ran longer than expected, along with some reported dissatisfaction with Hargitay in the role (ranging from her performance to how well she wore the costume) and Fitzpatrick returned. This actually resulted in discarding an extended sequence where Dulcea trains the Rangers in their proto-ninjetti powers (which are later seen in their fights), and they didn't have the time or budget to refilm with Fitzpatrick.
Adam being bummed out about being a frog was thrown in by Johnny Yong Bosch, who felt that it'd seem more real, and the fact that frogs aren't fast and agile, as he used to catch them in his backyard as a child. 
Directer Bryan Spicer, not having seen the actual series, pretty much did a quick "fast-fowarding" run of the series, ensuing things would go wrong.
When the Ranger suits were developed, the helmets were designed without visors or mouth pieces, intending on the heroes showing fear or worry. It wasn't until a little while later that Spicer and his crew realized that they were meant to be a fearless force to be reckoned with and they remolded the helmets to include those missing pieces.
Gabrielle Fitzpatrick, the original and final choice for Dulcea, was replaced partway by Mariska Hargitay. However, after filming her scenes, which included a training sequence, they felt she wasn't the right one for the job and they rehired Gabrielle, dumping all of those scenes.
The filming for the final scene at Darling Harbour where the team is thanked turned into a disaster area when local radio shows caught wind of it and tried to turn it into a "Meet the Power Rangers" contest.
Originally, Ivan Ooze was meant to mutate a bunch of rats for the Rangers to fight. However, the rat costumes proved to be too low budget even for the actual series, leading to the creation of the Ooze Men. However, the suits were spared and used in "The Return of the Green Ranger" three-parter.
Delays in the series forced the cast to remain in Australia for filming, forcing Saban to make the aforementioned "The Return of the Green Ranger" episode. This meant that six planned episodes, one of which would've feature the return of Scorpina, had to be jettisoned.
Steve Wang was originally planning to direct this film before Bryan Spicer took his place.
The film was originally planned to be shot at Warner Movie World/Village Roadshow Studios at the Gold Coast in Queensland, but it was booked for the Street Fighter film. However, with the help of Jon Landau, the crew used the Sydney Showgrounds, which would later become Fox Studios Australia three years after this film was made. Warner Movie World/Village Roadshow Studios would eventually become the location where the jungle scenes were filmed towards the end of its production.
The producers originally intended for the Rangers' masks to not have their visors and mouth pieces, feeling that it removed any sense of personality. They realized that their changes were counter-intuitive to the point of wearing a helmet because they were supposed to be an elite, faceless fighting force. They went overbudget and over schedule to refilm the necessary scenes. This actually resulted in the second season of the show overlapping with the film production (they were supposed to finish filming it when they returned home to America), the last few episodes were filmed in Australia.
Ivan Ooze was originally conceived as an animalistic and grotesque but charismatic creature inspired byKlaus Kinski's performance and character in Nosferatu the Vampyre, down to using an army of plague-ridden, mutated rat-men to brainwash Angel Grove's adult population into servitude; a Knight of Cerebus to exemplify the raised stakes the Rangers faced. This angle was dropped in pre-production due to fears of frightening the intended target audience, and the rat-men were later dropped and replaced with the Tengu warriors.
Austin St. John (Jason), Walter Jones (Zack), and Thuy Trang (Trini) were originally slated to appear in the film, but due to their contract dispute halfway through Season 2, they were dropped.
Catherine Sutherland (Katherine Hillard, the second Pink Ranger) auditioned to play Dulcea. Evidently they liked her enough to bring her to America for a role. Sutherland has lived in America since.
Mariska Hargitay was cast to play Dulcea after the original actress, Gabrielle Fitzpatrick, had to back out due to a scheduled surgery. The producers didn't feel that Hargitay was working out and was replaced with Fitzpatrick after she recovered. Due to budget issues, she wasn't able to refilm an extended sequence where Dulcea trained the Rangers in their ninja outfits at her home. As such in the movie the Rangers seem to just sit and stare at the monument for a time before deciding to go.
Dulcea's backstory was in the script, but cut from the film. It's explained that she is the sole survivor of an alien race who created the power in the Ninjetti Temple. She and Zordon were also members of the same order that imprisoned Ivan Ooze in the first place.
Ooze originally created a team of rat-men to battle the Rangers at the construction yard. Spicer and the producers felt they looked horrible and very low-budget (their goal was to create a high-budget looking movie) and such convinced 20th Century Fox to replace them with the more creepy looking Ooze-men. The rat-men costumes were later used in the "Return of the Green Ranger" three-parter on the TV series.
Instead of the gargoyles guarding the temple, the rangers would have fought another set of Tengu warriors - and their queen. The battle was supposed to happen on a long rope bridge on the way to the monolith. The set was built and put in front of a greenscreen but never used.
Dulcea would have had an annoying alien sidekick who picked on Kimberly. Around the time Fitzpatrick returned to play Dulcea, they decided to drop it.
The script developed as we were making it, and at one point the producer Suzanne Todd would be sitting in the corner on set, writing the script on her laptop. In the middle of speaking lines, I'd get handed rewrites, and a producer would say: "Here, say this instead".