During the third season, bloopers and extended scenes were often played during the end credits.
When the Alien Rangers appear to substitute for the Power Rangers, their episodes get their own opening credits.
Every time a new Ranger was added to the team, or a Ranger changed, or in some cases, the zords were changed, on-screen, the credits changed to reflect this alteration to the cast. This system continues throughout the series, with only Power Rangers SPD (It excludes Omega and Cat Ranger completely) failing to keep up with this.