Oh, this is for the writers? *missed that* Ok, wow, this changes the whole way I should have formatted this. PR is 17 seasons long (roughly 732 episodes, but I may have miscounted). Not all writers have seen every season, some only have a basic knowledge of some seasons. (My weakest season is Dino Thunder.) Zordon-era's not as bad because the cast changes weren't as abrupt, but from my list, we had an entire new cast (except for Tommy, who came back.) for each season.

Ok, off the top of my head:
Lost Galaxy: Damon Henderson, Kai Chen, High Councillor Renier
Lightspeed Rescue: Joel Rawlings, Chad Lee, Simon, Mr. Tamashiro, Vypra
Time Force: Eric Myers, Lucas Kendall, Trip Regis, Katie Walker
Wild Force: Alyssa Enrile, Max Cooper, Danny Delgado, Mr. Enrile, Toxica
Ninja Storm: Blake Bradley, Shane Clarke, Cam Watanabe, Kanoi Watanabe, Miko Watanabe, Kiya Watanabe (aka Lothor), Porter Clarke
Dino Thunder: Ethan James, Trent Fernandez, Tommy Oliver (back on active duty/mentorship)
SPD: Jack Landors, Z Delgado, Charlie, A Squad Pink (Fanon names her Rachel and the EP is on record as saying he likes it.), Dr Rheas.
Mystic Force: Madison Rocca, Vida Rocca, Daggeron
Operation Overdrive: Will Aston, Rose Ortiz, Dax Lo
Jungle Fury: Theo Martin, Luen Martin (Theo's twin), Master Mao (This was a pale, pale season, man.)
RPM: Scott Truman, Gem and Gemma, Colonel Mason Truman, Marcus Truman