I've been reading a lot of TV Tropes and got some free time so decided to cover some tropes (common writing themes used in popular culture) in Power Rangers. Since Power Rangers been running for almost 25 years and Sentai for 42, lots of plots have been reused. I will be covering Sentai later as there is a lot more series to go through.
Mighty Morphin (1993)
Billy and Kimberly switch bodies thanks to a machine Billy made. Bulk and Skull too. Since in the footage they didn't change bodies, there was no noticeable change other than in the dialogue.
In Space (1998)
Astronema has a monster kidnap Ashley and switches bodies with her. I think this was all new footage, not sure.
Ninja Storm (2003)
In "Sensei Switcheroo," Cam makes a device suppose to turn Sensei human again but instead switches bodies with Shane and then Dustin, which makes the Red and Yellow Rangers look like masters. This was all new footage and not from Hurricanger.
Against his will, Sky switches bodies with a criminal with a translator. This storyline was from the footage from Dekaranger.
In "Switching Places," the Rangers don't really switch bodies, their souls go into inanimate objects, which also happened in Shinkenger.
Super Megaforce (2014)
Jake and Noah switch bodies thanks to a monster, in Gokaiger it was Yellow and Green not Green and Blue, which was new footage.
Dino SuperCharge (2016)
The main 6 Rangers get their bodies switched by a monster like in Kyoryuger.
If there was more let me know.