Acting for Two: Jason David Frank has done this twice! Technically all the Rangers, since the original 5 played evil twin versions of themselves in a season 1 episode.
Actor Allusion: Rito had a tendency to call Zedd "Ed". The guy who wore the Zedd costume was named Ed Neil.
Author Existence Failure: Because of Thuy Trang's death in 2001, we'll most likely never see Trini unmorphed again (except in Stock Footage). Likewise, because of Richard Genelle's death, the odds of Ernie returning are nonexistant.
The Cast Showoff: Probably the most memorable examples would be Kimberly's gymnastics, for sheer longevity, but also her singing and guitar playing, Zack's singing and dancing, and a fair amount of Trini, Jason, Tommy, Rocky and Adam's martial arts.
Not to mention that David Yost (Billy) was actually a fair martial artist and talented gymnast, so his "bad" unmorphed fighting falls squarely into Irony As He Is Cast.
California Doubling: The Command Center, the Power Rangers' millenia-old headquarters created by Zordon in an undisclosed mountainous area near what would eventually become Angel Grove, California, is The House of the Book performance hall and library building at the American Jewish University, Brandeis-Bardin Campus in Simi Valley, California. It's shown up in quite a few other productions, including Star Trek VI: The Undiscovered Country, as the main building at Camp Khitomer.
Creator Backlash: Though very proud of her role as Aisha, Karan Ashley has spoken negatively about how her departure wasn't handled well. This is mainly why she turned down the offer to do a cameo in Power Rangers Super Megaforce.
An ironic case. Jason Geiger earned the Stage Name Austin St. John (inspired by The Six Million Dollar Man) as his agency thought it wasn't a strong name... and he ended up playing a badass called Jason. According to Tommy's actor Jason David Frank however, it was due to a disagreement the two had when they first met backstage.
Scorpina's disguise in "Goldar's Vice-Versa" was named Sabrina. The name of the actress who played her in the American footage was Sabrina Wu.
Dawson Casting: Do you honestly know any high schoolers that look that old? Well, out of the original five, Austin St John was 18 and Thuy Trang was 19, but Walter Emanuel Jones and Amy Jo Johnson were 22 and David Yost was 24. It would have been much more believable if their characters were written as college students.
Originally, the characters played by Austin St. John, Thuy Trang and Jason David Frank (who were all 19 at the time) were going to be plausibly the same age as the three aforementioned actors.
The second season wasn't as bad, but still fairly noticeable. Of the four (including Kat) replacements, Johnny Yong Bosch was 18, Karan Ashley was 19, Steve Cardenas was 20, and Catherine Sutherland was also 20. Add in the remaining 2, and you get another 20-year-old (Jason) and a 25-year-old (David). Before Kat, however, Amy was 23 and still on the show.
It wasn't just the rangers who suffered from this. Bulk and Skull were played by actors aged 23 and 19, respectively. It showed.◊
Direct-to-Video: Alpha's Magical Christmas, Lord Zedd's Monster Heads and The Good, the Bad and the Stupid: The Misadventures of Bulk & Skull.
Edited for Syndication: Episodes aired in Malaysia infamously had all occurances of the word morphin bleeped and airbrushed out. It's an embarrassing long story caused by some local soccer moms...
Executive Meddling: Not of their own choice but parents found Zedd to be too scary at the start (who could blame them, in the introduction in addition to his appearance. The guy had a snake wrapped around his arm.) Thus, the producers had to tone him down later to make him more of a laughable villain. It wasn't too much to dampen his character as he was still a force to be reckoned with however.
Lying Creator: In a roundabout way. The popular fandom rumor that Lokar appeared in the Bloom of Doom battle via stock footage to use his breath of doom on the Bloom of Doom to create "DeBloom" was started by Amit Bhaumik, who, while he didn't work on MMPR, was story editor for Power Rangers Wild Force. This rumor was debunked once and for all when Stunt Coordinator and editor Jeff Pruitt revealed uncut Zyu2 footage which revealed not only the Bloom of Doom (not Debloom) fight with Megazord and the lack of Lokar but that the Zyu2 footage didn't even feature stock footage (instead black screens appears to allow Saban to fill in with stock footage).
Mean Character, Nice Actor: Bulk and Skull were two jerkasses and wannabe-bullies (they sucked at being bullies); but their actors (Paul Schrier and Jason Narvy, respectively) are said to be some of the nicest and most fun guys you could ever hope to meet. One PSA even did An Aesop rather effectively about this. Of worthy note is that as the show goes on, Bulk and Skull go from being annoying jerks to comic relief, and as time passes even further, they go from okay guys to actual heroes.
The original Pilot was advertised and presented as such on Fox Kids. Notable changes include the casting of the Yellow Ranger as Audri DuBois as opposed to Thuy Trang, Zordon being known as "Zoltar", and the Zords being referred to as "Droids". There's also a second variation on the pilot, which Tony Oliver shows exclusively at conventions.
Zordon was voiced by David Fielding until "The Yolk's on You!", when Bob Manahan took over from "A Star is Born" onward.
The switchoff is notably different: Fielding used a terrible, cheap imitation of a British Accent, possibly to make Zordon sound more sophisticated. It's worth noting that Fielding was the one whose head we always saw as Zordon.
Rita's suit actress would be played by Carla Perez in season 2 with Barbara Goodson still providing her voice, in order for Rita to appear in American footage. Scorpina as well in "Goldar's Vice Versa" played by Sabrina Lu .
Lord Zedd was voiced by Robert Axelrod in the series, and by Steve Blum in the 2007 Playstation 2 video game Power Rangers: Super Legends.
The Other Marty: Audri DuBois was originally cast as Trini in the original pilot. Also Skull was originally played by an actor other then Jason Narvy; while he was not named in the pilot, his biker attire and crush in Kimberly identify him as the same character. However, Bulk and Skull's personalities were reversed in the pilot.
The Pete Best: Brad Hawkins was originally set to play the White Ranger, who was originally intended to be a new character separate from Tommy the Green Ranger. Due to Tommy's immense popularity on Power Rangers, Tommy was instead written back on the show as the White Ranger, while Hawkins was given the lead role on VR Troopers, which was originally intended to be a vehicle for Jason David Frank.
Postscript Season: Season 1 after "Doomsday". It was supposed to end with a shot of the Rangers sealing Rita away again, and is why Tommy makes a cameo appearance at the end. Most of the rest of the season was new footage created by Toei specifically for Power Rangers.
Prop Recycling: Old monster suits were often reused and altered in some fashion to create new monsters.
Mr. Ticklesneezer was painted blue and dressed in a Santa Claus-like outfit to become Grumble the Elf (who was more of a friendly elf creature rather than an evil monster - but then, so was Mr. Ticklesneezer).
Chunky Chicken had his feathers plucked and had armor and a helmet added to become Turkey Jerk.
Grumble Bee had his red sections painted silver and was given buck teeth to become Waspicable (a peaceful monster who didn't want to harm anybody) in Power Rangers in Space.
Pirantis Head, Robogoat, and Turbanshell were repainted and had a bunch of crap added to them to become random alien monsters in an episode of Power Rangers Turbo.
Primator was painted whitish and had extra fur added to him to become the yeti-like Snow Monster.
Salaguana was chopped into little bits and used as reptilian armor for Tritor, a heroic alien warrior from Power Rangers Zeo.
Silver Horns was painted green and had a tongue added (which is odd since he didn't really have a mouth) to become Repellator.
The Wizard of Deception's rat monsters were actually leftover, unused suits from the movie that were replaced by the Oozemen.
Inciserator was made up from the head of an unused Kakuranger monster and the body from Merrick the Barbaric (whose own episode hadn't even aired yet).
Tube Monster was actually Pipebrain painted white and blue with some slight alterations to the arm and head (although this one actually came Gosei Sentai Dairanger, not MMPR).
Real-Life Relative: Jason David Frank's real life son Jacob played the son of Rocky, Adam, and Aisha's Stone Canyon teacher whom Bulk and Skull looked after during "The Ninja Encounter" 3-parter.
Recycled Script: Two episodes in season three have the villains accidentally create a monster that can transform the Rangers into an object that ties into its theme. The monster proceeds to change every Ranger except Rocky into one and Rocky has to use his knowledge from chemistry class to change them all back. Making it even more obvious is that the episodes were produced and aired back to back.
Schedule Slip: The ABC reversioning had the Green with Evil 5-episode miniseries lasting over two months because sports always pre-empted the show And then the FIFA World Cup put the show on hiatus for yet another month.
The last four episodes were pre-empted on the West Coast for Little League. They can't be shown at a later date, because Nickelodeon took over the broadcast rights before the episodes could be re-scheduled.
Suffering For Your Art: Voice actor Barbara Goodson was getting jerked around by Saban during pre-production. She was given the part, and told to voice Rita like the Wicked Witch. She did, and was fired. They decided to try to make Rita sound angrier, and rather than let Goodson try, they forced her to reaudition. According to her, she did, and said, "You want angry? [Rita's screech comes out of nowhere] I'LL SHOW YOU ANGRY!" Not knowing she would have to do the part for seven years. She mentioned going through a lot of water and cough drops, and we thank her for suffering through.
Talking to Himself: In the French dub, Zordon, Goldar, and Tommy are all voiced by the same guy, Patrick Poivey, making most of Tommy's dialogue in the Green With Evil arc just Poivey talking to himself.
Technology Marches On: One episode had the teacher mistaking Tommy's communicator beeping with a pager. Nowadays, the only people who still use pagers are doctors and other hospital personnel.
Season 1 hit its troubles when it turned out the series was more popular than anticipated. So when Fox Kids ordered an additional 20 episodes for Season 1, Saban asked TOEI to make new fight footage from Zyuranger exclusively for Power Rangers, known to fans as Zyu2, due to the original usable Zyuranger being exhausted (even so, they made two episodes which recycled a lot of already used footage in different context to kill time until they got the Zyu2 stuff). The original plan was to do even more exclusive footage for Power Rangers and introduce upgraded Dinozords, but because of the cost, it was decided to just adapt Dairanger's monster and zord footage instead with only 25 Zyu2 fights filmed.
Season 2 had it even worse. The last ten episodes spilled over to Season 2, which created a new problem when Saban and Bandai wanted to introduce new zords to get new toys on the shelves in time for the holidays. The decision was made to hack the Dairanger mecha footage prematurely, resulting in two different sources of footage being spliced together for the zord battles. The mecha from Dairanger would launch an attack and then cut to footage of the Zyu2 monster taking the hit and vice-versa. After the Zyu2 footage was bled dry, the situation was completely reversed. Now, the monsters came from Dairanger, meaning the zord battle didn't have to be spliced together, but since most of the Dairanger monster costumes were unusable for American footage and Power Rangers continued to use the Zyuranger costumes, the majority of Dairanger monsters never once appeared on screen with the Rangers. Instead, most of the ground fights were Rangers fighting Z-putties in American footage with the Dairanger monster barking orders in completely isolated footage before Zedd made the monster grow. To top it off, Austin St. John, Thuy Trang and Walter Jones were let go halfway through Season 2 due to contract disputes with the producers and during the interim of writing the replacements into the show, the production team had to use stand ins and recycled footage from earlier episodes to make it seem like the departed cast members were still on the show until they were able to write them out.
When production ran longer than expected for the movie, the TV series production was forced to film in Australia, leading to heavy use of stock footage for scenes that required sets they couldn't access at the time, such as the Command Center.
Unfinished Episode: "Goldar's Vice-Versa" wasn't going to be Scorpina's last appearance, as there were plans for her to return later in Season 2 (in an 3-parter entitled "Zordon, I Shrunk the Rangers"), complete with confirmation that she and Goldar were indeed dating. However, due to the filming of the movie by 20th Century Fox going over schedule, they had to dump some episodes, including the three parter.
That same episode would have seen the return of Nimrod the Scarlet Sentinel and her assistants, AC and DC. The trio still had plenty of usable Sentai footage, including a scene where DC fights the Thunder Megazord on her own. This also would've made Nimrod and co. the only Dairanger monsters to be revived as one of Zedd and Rita's "best monsters of the past".
Unintentional Period Piece: It's a product of the 1990s and it shows. Not helped by characters (Kim and Bulk specifically) referring to it as "the 90s" at different times.
Urban Legend of Zelda: The long-persisting rumors of Lokar appearing during the unaired Bloom of Doom Zord battle were finally put to rest when stunt coordinator Jeff Pruitt released the unaired Zyu2 footage in February 2014.
At some point before Season 2, there were plans to introduce new versions of the Dinozords, as well as various different takes on the White Tigerzord (as can be seen by these pieces of concept art◊ from a Super Sentai Giant Robot artbook). These plans were aborted when it turned out that adapting mecha footage from another Sentai proved to be more economical for Saban than commissioning Toei to make more new footage for them
A redesigned version of Titanus the Carrier Zord was also planned to be introduced for Season 3. Various concept arts◊ were drawn, but Titanus was left mostly unchanged in Season 3 (aside for the addition of the Dragonzord's chest plate, since the Dragonzord was absent during Season 3). Some of those designs were made for Power Rangers in Space, and indeed a "Space Titanus" toy was in fact released, though it was never used in the show.
A Samuraizord, shown in the same image above with the Titanus redesigns, was considered for the second season as well. The Samuraizord would've been very similar to the Red Dragon Thunderzord, in which it could transform between a Tyrannosaurus and a humanoid robot.
Dan Southworth (Eric Myers on Power Rangers Time Force) stated at Power Morphicon that he had auditioned for the role of Adam during production of the second season. But instead, Johnny Yong Bosch got the role and Dan continued his stunt work. In addition to being Austin St. John's stunt double (morphed), he also acted as a stunt double to Johnny (also morphed).
At one point the writers actually considered having Goldar eventually overthrow Rita instead of creating Lord Zedd.
In earlier scripts, Tommy was going to be a biker named Rocky.
An early pitch reel has been uncovered and put on one of the Shout! Factory DVDs. The show would be called Galaxy Rangers (which was Zyuranger's international title). The characters were going to be: Victor Lee (Red Ranger), an Asian martial artist. Zack Taylor (Black Ranger), a detective with an attitude. Kimberly Harte (Pink Ranger), a clumsy aerobics instructor. Billy Cranston (Blue Ranger), an athletic heartthrob with a body of steel. Trini Crystal (Yellow Ranger), a struggling, white novelist. Note how Zack is described as "green", and how all five are designated "Biorhythm (color)"- this, along with the 80s attire and aged-looking American footage, would suggest they cannibalized this from their failed pilot for an adaptation of Choudenshi Bioman in 1986.
The original finale (written before the show took off) would have seen Rita crashing the Ranger's senior prom; Saban was even looking into bringing Machiko Soga over to the States so she could physically interact with the Rangers at the Juice Bar. It would have ended with the rangers Storming the Castle after getting access to Rita's spells and Jason reciting an incantation to seal her away, but the show continued after it was a hit. Tommy's cameo was a relic of this original plan as...
Jason David Frank was going to be in VR Troopers (called Cybertron at the time) and shot a pilot of it. After Power Rangers was picked up for more episodes Brad Hawkins was cast as the White Ranger, Saban decided that it was too risky to replace Frank now that there was the opportunity to bring him back, so Hawkins went onto VR Troopers and Frank returned to Power Rangers.
Ernie was originally going to be Zordon in disguise, watching over the Rangers from the Juice Bar.
As shown in the unaltered Zyu2 footage provided by Jeff Pruitt, the Pirantis Head Zord battle would have had the piranha monster use his flute to re-take control of the Dragonzord and use it to help himself fight the Megazord, with the footage implying that Titanus would come to the rescue.
Before David Yost got the part, Jason Narvy was initially offered the role of Billy during auditions.
Original names for Goldar, Squatt, and Baboo were Dredwing, Grock, and Mongo.
Had Mighty Morphin only been a moderate success, aside from the aforementioned original finale being used, it's likely that instead of commissioning the Zyu2 footage for season 2, Saban would've done more straightforward adaptations of Dairanger and Kakuranger.
You Look Familiar: Series writer Doug Sloan played Kimberly's Uncle Steve in "Foul Play in the Sky" and her mother's new boyfriend in "Return of an Old Friend". Its somewhat popular in fanon that they're the same person and Kimberly's mother left him for his brother. (As a side note, he also played Tyler Steele in the above-mentioned Cybertron pitch reel.)