The Alien Rangers, also known as Aquitians, reside on the planet Aquitar. However, their native planet isn't exactly peaceful. A being known as Hydro Hog, emperor of the Dark Waters, is constantly attacking the Rangers. No victor has ever been decided on in their battles since both sides are very evenly matched, but the Rangers defense is enough to hold off Hydro Hog.
Meanwhile, the planet Earth is protected by the Power Rangers. They were able to stop the continuing onslaughts from Rita Repulsa, Lord Zedd, and Master Vile on over one hundred different occasions. When the Rangers were turned into children by the Orb of Doom though, they were no longer able to morph and fend off the incoming evils. This is when new heroes needed to be called upon. Zordon contacted the Alien Rangers, who came to Earth's aid at once.
The Alien Rangers fought bravely against a plethora of monsters, sent down mostly by Lord Zedd. On several occasions, Zedd came close to victory, but could never quite get the Aquitians number. Using their Battle Borgs and the Shogun MegaZord, the Rangers destroyed all monsters. Finally though, Zedd and Rita got smart. They brought Hydro Hog to Earth. This proved near fateful for the Rangers, as their prime nemesis beat up on them at will. The Hydro Hog even held off the Shogun MegaZord's fire sword attack, which is what the Rangers had used to defeat most of the monsters. Drastic measures had to be taken, and that's exactly what happened. The White FalconZord was called into action, and it combined with the Shogun MegaZord to form the Shogun MegaFalconZord which made quick work of Hydro Hog, and kept the Earth safe.
After that battle, the Rangers were finally able to grow back to normal size using their newly acquired powers derived from the Zeo Crystal. This is when the Alien Ranger's services were no longer necessary. Both sets of Rangers said an emotional good bye to each other and the Alien Rangers returned to their home planet, Aquitar.
Also, there was another point in time in which the Power Rangers Zeo were going through a time of sorrow. Billy was getting very old, almost to the point of dying, and even Zordon did not know what to do. So the superior intellectual minds of the Alien Rangers were called upon to help. This was not the only problem though. King Mondo had sent his cogs and his Cog Changer to Earth while Lord Zedd countered with the Impursonator. These were overwhelming forces for the Zeo Rangers, so the six of them tag teamed with the five Rangers of Aquitar to form an unbeatable team. They all fought bravely against the cogs and monsters, and soon enough, the monsters grew to galactic proportions. Using a divide and conquer technique, the Zeo Rangers trounced the monsters in their Zords while the Alien Rangers dominated the cogs, displaying the tremendous versatility of their fighting skills. When all was said and done, the whole lot of Rangers regrouped on the ground and the team leaders gave their thanks to each other. Again, the Alien Rangers had lent a tremendous hand in saving the day from evil.