In the original Japanese footage, the Yellow Ranger was male. This is why the Pink Ranger has a skirt, but Yellow doesn't.
The character Kimberly Ann Hart was originally meant to serve as a stereotypical "dumb blonde"-type character. When Amy Jo Johnson was cast, the character was changed to a Valley girl-type and she actually made several contributions of her own to her character as the series progressed, including Amy Jo's real-life gymnastic skills and being able to play the guitar.
Austin St. John, Walter Jones, Thuy Trang, and Jason David Frank were all martial artists long before the show. Amy Jo Johnson and David Yost were gymnasts who had never done martial arts before. They took self defense classes and incorporated their talents into the fight scene choreography.
Jason David Frank (Tommy) was never meant to stay on the series for as long as he did. He was only supposed to be a regular until "The Green Candle Part 2" minus a cameo in "Doomsday Part 2." but during his temporary time on the show his popularity was higher than any other Ranger. Saban received large amounts of letters daily after "The Green Candle" requesting Tommy to be brought back into the series, Eventually the company gave in and brought Frank back in the episode "Return of an Old Friend." and ended up staying on the show lasting till Power Rangers Turbo (1997) and recently in returning for Power Rangers DinoThunder (2004). He has appeared in a total of 217 episodes in the entire Power Rangers series.
Lord Zedd is the very first Power Rangers villain to be American made instead of appearing originally in any Super Sentai production.