Plot hole: During the Green Candle, in series 1, we are told that the only reason Tommy's Green Ranger powers could be drained is because he touched a special wax. However, Kim, Billy, Zack, and Trini did not touch the special wax, therefore the candles shouldn't have stolen their powers. When they were captured, they were transported straight to a prison cell as Goldar lit the candles, therefore the Rangers couldn't have touched the candles when captured.
Continuity mistake: This can only be seen for a few frames, so slow motion may be needed. Tommy reveals himself as the White Ranger by unclipping his helmet; however, his ponytail is already visible. Tommy's hair should have been inside his suit/helmet if he had just unclipped it. From behind shots, it is tucked in.
Factual error: Billy, Kim, Rocky, Aisha, and Adam return to Angel Grove in the 1700's...and there are British Redcoats there. On the West coast, in California. England never deployed troops to California, especially considering it was part of the empire of Spain at that time.
Other mistake: The Tigerzord has various orbs behind the White Ranger, that give the Tigerzord various abilities. The only one we ever see used is the one for a Fireball. For the rest of the series, this orb disappears and reappears, whether the Fireball has been used or not.
Deliberate mistake: A few deliberate mistakes here. It was around this time that 3 of the actors on the show (Austin St. John, Walter Jones, and Thuy Trang; who played Jason, Zack, and Trini) walked out over pay issues. So, to work around this until replacement rangers could be found, Saban used old footage of the 3 that walked out. The mistakes are as follows: 1) Tommy is shown to be wearing green. The Rangers wore clothes that matched the colour of their powers - Tommy was now the White Ranger (and should be wearing White clothing), as the Green Ranger powers had been destroyed. 2) Zack's hair changed from dreads, to his flat cut. This had an instant effect on Kimberley and Tommy's hair (again, due to the old footage), which had gotten noticeably longer as the series progressed. 3) Jason, Zack, and Trini's voices were different when they were morphed - obviously, they were voice sound-a-likes.
Revealing mistake: Certain monsters in Zord battles were designed for the first series. This is so Saban could use Japanese footage of ground fights, to save on shooting their own (As the costumes from series 1 carried over into series 2). Sometimes, you can see the Megazord, and Dragonzord, getting attacked (you may need to pause it). It should be the Thunderzord, or Tigerzord.