Over three seasons, the format of the show rarely changed. Although the Green Ranger was evil at first, he eventually joined the Power Rangers as their sixth member, and from then on they battled Rita and her Putty henchman every week. Beat the Putties, lose to her more powerful henchmen, get in their Zord form, beat the henchmen, lose to Rita, become Megazord, beat Rita. Every. Single. Week.
It wasn't much of a challenge for either the viewers or the actors, but both parties were clearly having the time of their lives. We loved it because we knew exactly what was going to go down, in the cheesiest way possible, and the cast loved it because it was basically them getting paid to hang out as best buddies all day.