Once a Ranger

Once a Ranger is a special team-up episode in Operation Overdrive involving Power Rangers from five different former generations (collectively known as veteran rangers) assisting the Overdrive Rangers in defeating a new threat: Thrax. The title of the episode is a blatant reference to the long-standing phrase "Once a ranger, always a ranger."

Part 1
Thrax—son of Rita Repulsa and Lord Zedd—is freed, and he recruits all the villains who have been searching for the Jewels of the Corona Aurora—Flurious, Moltor, Kamdor, Miratrix, and the Fearcats Mig and Benglo—to unite with him temporarily. By severing their connection to the Morphing Grid forever, the temporary Evil Alliance destroys the Rangers' powers, and Andrew Hartford cannot fix their destroyed morphers. They use their enhanced skills in an attempt to defeat the villains, but fare no better, so the Sentinel Knight recruits five Rangers from the past—Kira Ford, Xander Bly, Adam Park, Bridge Carson, and Tori Hanson—to replace the Overdrive Rangers until their connection to the Morphing Grid is restored.

Part 2
The villains in Thrax's "Evil Alliance" are angry, because Thrax did not think there would be more Rangers.

Meanwhile, Mack Hartford is searching for information on the sword Excelsior—which Thrax says is the only thing capable of eliminating the Sentinel Knight. He tries to retrieve the sword, but is confronted by Thrax, who intends on saving the legacy of his family of Evil. He is unable to claim the sword for himself, so he sends a giant monster named Vulturas into the city to destroy it. The Retro Rangers head him off in the DriveMax Ultrazord and Flash Point Megazord, but are overpowered, and DriveMax Ultrazord loses an arm in the battle.

Meanwhile, Mack convinces the Rangers that they will always be Rangers, powers or not, and they all attempt to free Excelsior from the Warrior-Goddess's hands. The statue comes to life and gives them the sword, sensing the shared friendship and combined conviction in their hearts. Then, Mack heads to the battlefield, where the Retro Rangers are about to be destroyed, and uses the sword Excelsior to destroy Vulturas. Meanwhile, Adam reactivates Alpha 6 and teleports him inside the Morphing Grid, where he fixes the severed connection, restoring the Overdrive Rangers' powers. Mack hands Sentinel Knight the Excelsior sword, which gives the Knight a Cyborg form.

Confronting the "Evil Alliance", all 11 Rangers morph and battle the villains. Adam battles Thrax. Bridge and Mack team up to defeat Flurious. Dax, Will and Xander defeat the Fear Cats. Tori and Rose battle Moltor and his Lava Lizards, and Kira and Ronny team up against Kamdor and Miratrix. Tyzonn is able to destroy the newly revived Vulturas and Flurious's Chillers. To finish the battle, the Sentinel Knight arrives in his Cyborg form and destroys Thrax, and then joins the Rangers in defeating the rest of the villains.