Doomsday

Doomsday was a two-part episode of Mighty Morphin' Power Rangers that aired in 1993, on November 23 and November 24, consecutively. It is the episode noted for introducing the concept of Zords piloted by antagonists to American audiences, a trait that would continue in various subsequent seasons of Power Rangers.

Plot
While the city of Angel Grove celebrates the Power Rangers, Rita Repulsa makes her boldest move yet when she transports the entire population to another dimension. Enlisting the malevolent Lokar and the evil war zord Cyclopsis, Rita overpowers the Rangers and nearly destroys their zords. In the end, the Rangers discover Cyclopsis's weakness and foil Rita's plans once again. Zordon offers the Rangers the ability to give up the power and return to their normal lives, but they unanimously choose to stay on.

Part One
The Mayor of Angel Grove declares the first ever "Power Ranger Day", and the city marks the occasion with a large gathering in the park. Rita Repulsa, meanwhile, hatched her biggest scheme yet: she will bring her Lunar Palace to Earth, greatly increasing her power, and call on the long-dormant war zord Cyclopsis to defeat the Power Rangers once and for all.

In Angel Grove Park, a large crowd turns out for a special appearance by the Power Rangers, but Bulk and Skull show up as the "Incredible Bulkster" and "Super Skull" in an attempt to steal the spotlight. As Rita lands her palace in the heart of downtown Angel Grove, everyone in the city is transported to Rita's dark dimension.

After being briefed by Zordon on the extremely dangerous situation, the Rangers morph and teleport to downtown Angel Grove and summon Megazord to fight Cyclopsis. The Megazord proves unable to match up, so they summon Dragonzord to boost their power. Despite attacking in every battle mode available to them, the Rangers are unable to finish off Cyclopsis. Zordon finally calls on Titanus and the Rangers form Ultrazord, which succeeds in destroying much of Cyclopsis, but its head remains intact. Rita then instructs the evil Lokar to revive Cyclopsis.

Part Two
Rita's assault continues while the Power Rangers are forced to bide time as the zords recharge. Jason decides to take the zords back into battle, even at half power, over Zordon's and Billy's objections. The group returns to the city with Megazord to face Cyclopsis again, but in its weakened state, it is overwhelmed even more quickly than in the previous battle, losing an arm in the process. Jason summons Dragonzord as backup, but it too is low on power, and Cyclopsis severs its tail. With both Megazord and Dragonzord down, Rita takes direct aim at them with her staff, overloading their systems. The Rangers are forced to evacuate as the zords disappear piece by piece. Despite fearing the worst, the disappearance of their zords was actually a security override designed to return them to their hiding places in the event they were ever close to being destroyed.

The Rangers are involuntarily demorphed and land in a still deserted Angel Grove Park, where they are unable to use their communicators to contact the Command Center. They went to Billy's lab, where he works feverishly to retune the communicators. Before he can finish, Goldar arrives with a group of putties, intent on destroying the Rangers while they're at their weakest. At the same time, Alpha takes the opportunity to hack into Rita's databanks while her palace is still on Earth. While doing so, he uncovers Cyclopsis's weakness.

Billy completes his work and the group teleports to the Command Center just before Goldar could attack. Zordon then reveals Alpha's critical findings to the Rangers: Cyclopsis must adjust its systems to compensate each time the zords change configurations. Zordon believes if the Rangers change modes frequently enough, Cyclopsis will become overwhelmed and vulnerable.

With the zords fully re-energized, the Rangers morph and teleport to the city, call for their Dinozords, and attack individually. They then form the Megazord and Dragonzord in Battle Mode in rapid succession. Cyclopsis is still dominating, but the Dragonzord manages to sever its bladed hands. After taking another energy blast from Lokar, the Rangers summon Titanus and once again form the Ultrazord. Zordon's hypothesis proved correct, and Cyclopsis was unable to adjust to the frequent changes. Goldar is forced to bail out of the cockpit just before Ultrazord obliterates Cyclopsis. Lokar escapes before the Rangers can turn their attention to him. Humiliated again, Rita and her Lunar Palace return to the moon.

Back in the park, the people of Angel Grove are returned from their other-dimensional prison with no knowledge of having been transported there in the first place. The Rangers arrive to much fanfare. While a group of children discuss their favorite Rangers, Tommy Oliver clues them in to a secret: "They're all totally awesome."

In the wake of their toughest battle yet, Zordon thanks the Rangers for their dedication and offers them the chance to give up the power and return to their everyday lives. All five choose to remain Power Rangers.

Production History
Doomsday was originally intended to be the final installment of Mighty Morphin Power Rangers. The Toei footage from these episodes was taken from Zyuranger's final episodes.

After MMPR became an instant hit, Fox ordered twenty additional episodes, and Doomsday's plot was presumably altered to allow the series to continue on.

Having exhausted footage from actual Zyuranger episodes, Saban entered into an agreement with Toei to produce all-new battle scenes that would be used throughout the remainder of the first season and well into the second.

Errors

 * When Rita first summons Cyclopsis, her wand is shown firing a blast that flies to Earth from outer space. However, her palace had already landed in Angel Grove.
 * At the beginning of part II, Alpha said the zords would need 12 hours to completely recharge from the first fight with Cyclopsis. After the zords' emergency evacuation during the second battle, they are said to be fully recharged and repaired just a short time later.
 * The Triceratops growled like the Tyrannosaurus before its tail retracted for the Megazord Tank Mode assembly.
 * While Zordon is explaining how to counter Lokar and Cyclopsis, you can see the upper parts of three people looking up at it, even though the entire population of Angel Grove was trapped in a vortex.