Rocket Raccoon’s origins are not for the faint of heart, nor are they common knowledge among even dedicated readers of Marvel Comics. The publication of Rocket Raccoon comics was sporadic at best until 2014’s Guardians of the Galaxy made him into an A-lister, so there’s surprisingly little continuity behind the character - despite him having been around for decades. And what continuity does exist is about as weird as it gets.
Rocket’s backstory has been hinted at in both Guardians of the Galaxy movies, but his full origin likely won't appear in the Marvel Cinematic Universe. Rocket’s history in the Guardians comics includes toy factories, a cosmic asylum for the mad, an otter girlfriend, and a bounty of other incidents that would be too bizarre to translate to the big screen. Of course, his comic book canon also contains some of the greatest Guardians of the Galaxy stories ever told.
The true first appearance of Rocket in Marvel Comics is somewhat debatable. A character named “Rocky Raccoon” adventures alongside Prince Wayfinder in 1976’s Marvel Preview #7 written by Bill Mantlo and drawn by Keith Giffen.
The angry, cigar-chomping Rocky bears a striking similarity to the modern Rocket, but he’s technically a distinct character and not a part of official Marvel canon. Six years later, Bill Mantlo - head writer for Incredible Hulk - re-invented Rocky to fold him into mainstream continuity.
Rocket’s home planet is named Halfworld, and it has a complex history. As a world within the Keystone Quadrant, Halfworld was settled by the unnamed group of humanoids that populate that sector of space. They came to Halfworld intent on building an asylum to treat the litany of mentally ill individuals apparently present in their interplanetary population.
A number of Earth-like species are native to Halfworld, and so the original settlers - known colloquially as “Shrinks” - put them to work as therapy animals for the patients. The creature that would become Rocket starts his life in such a capacity and without any of the trademark wit and intellect that would one day define him.
Little is known about the interplanetary civilization that built the enormous asylum on Halfworld, only that their funding was cut at some point and they were forced to abandon their project. But rather than shutting up shop completely, the Shrinks left their planet of patients in the care of robot psychiatrists.
The robots eventually become independently intelligent and move to the other side of the planet to completely industrialize it, leading to the two-toned appearance that gives Halfworld its name.
Before abandoning their job as caretakers, the now-sentient robots take the time to ensure the asylum's inhabitants are looked after. They do this by using genetic engineering to experiment on the patients’ therapy animals, granting them greater intelligence, awareness, and physical capabilities.
Though the former therapy animals now possess intellect roughly on par with human beings, they aren't left with much information upon which to build their culture and civilization. The Halfworlders are forced to base their entire existence around the role they were created for - taking care of patients and maintaining the peace on their half of the planet.