The Octalians are the major antagonists of the second season of the Disney XD series Milo Murphy's Law. They are extraterrestrial cephalopods (led by the Octalian Commander) obsessed with Milo Murphy and his negative probability ions that they intend to use for their own plans which was to save their homland from destruction.
Managing Murphy's Law
The Octalians first appeared commandeering their ship to Earth when the Octalian Pilot informed the Commander of a series of glitches caused by Murphy's Law, due to the presence of a boy named Milo Murphy attending a gig for an incoming concert. Seeing that there are many negative eons surrounding the boy due to Murphy's Law, the Commander orders her ship to follow him.
As such, the Octalians flew over to Milo's house, but Murphy's Law started more glitches in the system, causing the ship to go out of control, incinerating the Murphys' garage (though Milo and his friends manage to escape the damage). The Pilot tried to convince the Commander that they should move away from the area, but the Commander demands to get closer to Milo as she wants more info. During the concert, the ship goes out of control again, which finally forced a nervous Commander to tell the Pilot to move their ship away from Milo, saying that they would have to wait another day to get closer to him.
The Octalians witnessed Balthazar Cavendish ranting out about the existence of aliens after being kicked out from the Danville Community Center for his ramblings. Seeing that Balthazar's suspicions may expose their presence to the world, the Commander orders the Pilot to fire a laser to incinerate Balthazar to cover their tracks. However, another laser beam (fired by Heinz Doofenshmirtz) hits the ship, causing it to set itself into autopilot and fly away from Earth's atmosphere back to their home planet, much to the Octalians confusion.
Getting her ship to be parked at a safe distance from the Murphys' residence, two Octalian agents Loab and Khone were sent to spy on Milo. Though Loab and Khone are able to infiltrate into Milo's house without being spotted by the Murphys, they end up being caught by Milo's dog Diogee, who angrily barks at them. After a series of mishaps (due to Murphy's Law) inside Milo's room and being attacked by Diogee, the duo is forced to escape back to the ship, prompting the annoyed Commander to do the job herself. To that end, she posed herself as Milo's mother Brigette while meeting Milo in his room, allowing herself to obtain a tissue sample before escaping back into her ship. The Commander was glad to finally obtain the sample and decides to make her next move of kidnapping Milo, but she is distraught to learn that she has caught a common cold since she touched Milo while getting the sample.
Abducting Murphy's Law
With Milo's DNA, the Octalians created an android doppleganger of Milo to take his place while they take the real Milo and confine him in their ship. The Commander is about to explain her actions and plans to Milo, but Murphy's Law caused all of the Octalian's communicators to malfunction, making Milo believe that the Octalians are planning to eat them. Because of this, more glitches wreak havoc in their ship, allowing Milo to escape through the ventilation systems. The Commander then sets out her soldiers to go into the vents and capture Milo, but Murphy's Law only made things even worse as they end up being trapped in serious situations that they are unable to escape from.
Fortunately, Milo arrives to the rescue by using his backpack to provide solutions to free several of the Octalians from danger, and they explained the events to the Commander, who decided to transport Milo to their homeworld for some obvious reason. Unfortunately, Milo's ions caused the ship's main console to malfunction, causing their ship to crash towards Earth. While Milo is accidentally jettisoned from the ship due to decompression (though he is saved by Doofenshmirtz, Zack and Melissa), the Octalians are forced to leave on an escape pod to avoid the collision.
Though it would seemed the Octalians are gone, the Milo android stated to Milo and his friends that the Octalians will return sooner or later.
Milo in Space
The Octalians returned with a fleet of ships to capture Milo once again, but Murphy's Law comes into effect, destroying all of the ship except for the mother one. After getting Milo and the Octalians on board her ship, the Commander reveals her true motives: their planet Octalia is in danger because of a giant but dangerous sphere of negative probability ions and that they need Milo's help to stop it due to his knowledge in Murphy's law. Realizing now that the Octalians are actually in desperate need to save Octalia, Milo agrees to help out in this.
Sphere and Loathing in Outer Space
It is revealed that the Commander has a daughter named Orgaluth, who happens to be the unexpected source of the dangerous sphere threatening the Octalian planet. The Commander explained that just like Milo, Orgaluth had been experiencing bad luck ever since infancy and that she is unable to control it. Fortunately, Milo brings in his friends (including Doofenshmirtz) and they utilized Doof's new inator called the Reduce-inator to decrease the effects and pass it over to all the other Octalians to destroy the sphere and avert the crisis for good.
With the sphere gone and the planet safe once again, the Octalians are relieved while the Commander happily hugs Orgaluth and allows Milo and his friends to leave back to Earth.