Maximillian Acorn was crowned King of Mobius during the Golden Age, with his seat of power being the Kingdom of Acorn. Max also took Alicia Acorn as his wife, fathering two children; Elias Acorn and Sally Acorn. Max led his people in the Great War, and during so was duped by Overlander defector Julian Kintobor into making him Warlord of his combined military might, and as such, upon the war's end, was betrayed by Julian, who christened himself "Dr. Ivo Robotnik", and banished to the Zone of Silence. After many years in the Zone, where he was forced to become subservient to the wizard Ixis Naugus in order to survive, the Knothole Freedom Fighters, led by Sally, finally found and freed Max, who resumed command of the Kingdom of Acorn shortly afterwards. The strain of all these conflicts, battles with Robotnik and Eggman, and three attempts on his life, have all taken their toll on Max, eventually to the point he prematurely aged, and was left in no condition to lead, leading to Elias taking his place. While his condition seems to continue to degrade, Max remains a vital member of the House of Acorn. The tragedies that befell the kingdom during his reign led to his reception of the sad title of Maximillian the Cursed.
The King (no other name given in this continuity) was the ruler of Mobotropolis, until the evil genius Dr. Robotnik took over and banished the King to the barren interdimensional realm known as the Void. Sonic and Sally later used the Time Stones to travel back in time, meeting him and warning him of the threat, but they were unable to save him from this imprisonment, for it was the very same day that the coup took place. Worse yet, the King was not alone; the Void was also the prison of Robotnik's mentor Naugus, a dark wizard of great power.
Sonic and his allies managed to enter the Void years later, finding the King alive and well. However, he only escaped the Void for a brief time with them before his body began to crystallize as a result of years of exposure to the Void's strange environment. As a result, he was forced to return there, much to the dismay of the Freedom Fighters and Sally in particular. However, they did benefit from the brief meeting: not only did they rescue the King's fellow prisoner Ari, but they also received a list of all their ally groups.
Had the series not been canceled, the King would have escaped the Void along with Naugus, and been used by the wizard as bait to lure the Freedom Fighters into a trap.
The King's personal timeline in the series has some inconsistencies. He was imprisoned in the Void on the same day as Robotnik took over Mobotropolis, but he also later possesses a list of all Freedom Fighter groups, which did not exist when he was banished. Additionally, the first season episode "Sonic Boom" indicates that he was until recently held in Ironlock Prison, from which he transmitted sensitive documents to his daughter - an event that is totally incompatible with what would later be revealed as his fate.
The series echoed SatAM in the fact that both King Acorn and Ixis Naugus were banished, but to the Zone of Silence rather than the Void. While in the Zone, King Acorn was forced to pledge loyalty to Ixis Naugus to survive. Over time, he lost his memory, not recognizing Sonic or Sally when they came to the Zone. He came to command an army of goblin-like creatures, clad in a barbaric suit of brownish-purple armor and claiming the Zone as his domain with an iron fist.
Later, the Freedom Fighters managed to free King Acorn from the Zone and brought him back to the safety of Knothole Village. Unfortunately, the King's body soon began to crystallize, apparently due to prolonged exposure to the Zone's harsh, alien environment (similar to the situation that occurred during SatAM). It was then discovered that the Sword of Acorns, when brought together with the Crown of Acorns and the King himself, possessed powerful healing properties and was able to restore King Acorn to his former self. It later became known that the wizard Ixis Naugus had been responsible for the King's condition, forcing Sonic to confront him and his minions-Warlord Kodos, Uma Arachnis, and Feist-in Max's dreams.
At one point, King Max was secretly replaced by one of Robotnik's Auto-Automatons, robots that are virtually indistinguishable from the living beings they're designed to imitate. While impersonating the King, the robot unilaterally sentences Sonic to life in prison in the Devil's Gulag prison when Sonic is mistakenly charged with the murder of Princess Sally. He also later brings Robotnik himself to Knothole, where Robotnik reveals that the King was a fake.
Following Robotnik's defeat, it came to light that King Max had been hiding the existence of other members of his family from Sally. These relatives were his wife Alicia and his son Elias. Shortly before Robotnik's takeover, the two of them had been sent into hiding, only to disappear and crash land on Angel Island. Found by the Brotherhood of Guardians, the young prince and comatose queen were cared for until they were eventually returned to Knothole. Alicia awoke shortly after this, but Max found himself paralyzed from the waist down. This necessitated his use of a wheelchair to get around. For unexplained reasons, he recovered from this condition during Sonic's Xorda induced, year-long exile in space.
In his Acorn One, Max led the Kingdom of Knothole in the first years of its ever-raging quest to defeat the Eggman Empire. He was not well liked among the Freedom Fighters at first because of his arrogant decisions, which included disbanding them in favor of his own Secret Service (though he later had the Freedom Fighters reinstated), trying to force Sally into an arranged marriage with Antoine D'Coolette, and denying Sally her birthright, title and duties if she refused. This is later revealed to be the result of his mind being half-crystallized, a side effect of time spent in the Zone of Silence.
King Max was poisoned by Patch, the Anti-Mobius version of Antoine, whom he was impersonating at the time due to an exchange brought about by Scourge the Hedgehog. The king slipped into a coma, forcing Prince Elias to take the throne to keep Patch from becoming King. Some time afterward, Max was revived by a device powered by a Chaos Emerald, though apparently confined to a wheelchair once more. He was among those captured during the destruction of Knothole and was beamed to the Egg Grape Chamber, only to be saved by the efforts of Sonic, Knuckles the Echidna, Tails, Amy Rose, and NICOLE, who saved the prisoners by having NICOLE transport them to the city of New Mobotropolis. When his old general Amadeus Prower rebelled against the monarchy, Max was outraged, denying Amadeus' criticism of the House of Acorn and extolling royal line despite the merits of Amadeus' accusations. Moreover, he used the opportunity-and Amadeus' short imprisonment-to try and plant mistrust of Sonic in Elias' mind. Influenced by his father, Elias ended up facing Amadeus in a duel, which was luckily brought to a halt by Sally, who settled the differences of the two and worked with them to create a new form of government. The new system of a ruling council in which the king served as a presiding councilor with six elected peers was received warmly by everyone-except for Max, of course, who became moody and refused to acknowledge his son after the news became public.
Max began to show an increasingly distant and reclusive attitude some time after the Iron Dominion takeover, causing concern from his wife. It eventually became clear that he could not accept the new form of Republic, eventually deciding to speak with Geoffrey St. John, tasking the commander with finding a way to return the monarchy to "proper authority." Geoffrey convinced the former king he thought of a plan, and the former King granted permission for him to find any mean necessary. Later, when his son Elias inquired to Doctor Quack if Max was plotting to take back the throne, the doctor dismissed the allegations, stating that Max's current condition has prevented him from being a significant threat to anyone, and his "good days" were becoming even more infrequent with time.
Unfortunately, Max's decision in entrusting the task to St. John had been a failure. Geoffrey was revealed that since his childhood, he had been secretly affiliated with the Order of Ixis's remnants as an apprentice wizard. His master was none other than Ixis Naugus, whom St. John decided to return to glory by granting a Chaos Emerald in order to restore Naugus' sanity. Upon this, Naugus and Geoffrey arrived in New Mobotropolis a few days later, Naugus with the intent of finally claiming the crown for himself. Aside from recently growing fear of NICOLE in the public (after she was possessed during the Iron Dominion's invasion of the region), Naugus also based his claim on his past interactions with Max, despite Elias's arguments. The Freedom Fighters, meanwhile, attempted to stop Naugus from the claiming of the throne, but an assault by Eggman conflicted with the plan.
The chain of events that followed had disastrous consequences for all participants; Eggman's recently-launched Death Egg Mark 2 was severely damaged by the explosion of the World Roboticizer, and was forced to retreat. However, in this process, he had gained a new servant when Sally sacrificed herself to be roboticized in order to prevent the mad doctor from destroying the world - the first of multiple crushing losses the Freedom Fighters would suffer over the next few days. Worse still, without Sally's leadership and diplomacy skills, Elias was successfully dethroned, and Naugus was crowned king - a change instantly accepted by the common people. As Sonic & co. continued to try and stop the wizard, Elias went home to tell his parents the bad news.
Max, regardless of his condition, was as deeply shocked by the recent events as almost everyone else. Shortly thereafter, Elias decided he and his family were no longer safe in the city and attempted to convince his parents to join him, but Max couldn't go due to his condition, and his wife did not want to leave him. His options running out, Elias went to see Harvey Who, whom Max had told him was always there to "watch his back". Harvey, though, had come to consider Max crazy for not originally following his advice, and consequently refused Elias' aid at first. However, the old owl changed his mind upon seeing that the boy was a better ruler than his father. The next day, Max was present to watch his son's departure from New Mobotropolis. Before long, though, Elias would secretly return as part a team of covert new Freedom Fighters formed by Harvey to take the kingdom back from Naugus. Max was later shown asleep in bed, with his worried wife at his side and his son watching from the shadows. It is not exactly clear at this point whether or not Max's condition had improved or worsened, but obviously the old ex-king was not looking any better than before.
When Naugus began to feel ill, due to the presence of the three former Ixis Wizards-who created Naugus himself-haunting his mind, he began to show inner and outer body problems, after a ceremonious attempt to mutate himself, halted by the Secret Freedom Fighters. In desperation, he sought out to possess a Mobian's body to avoid the mutation. He first consulted with Maximillian, stating that he could heal him using his Crystalline magic (though he was actually lying, instead seeking out a victim). Maximillian directly refused, and Alicia kicked Naugus out before he could raise an argument. After Naugus left, Max tearfully thanked his wife for backing up his statement.
King Acorn also appeared in a future storyline where Sonic and Sally are married as King and Queen, and where he is a grandfather. This version of the future is where NICOLE originated. He does not appear in the Mobius: 25 Years Later future, possibly having died at some point between the present and the possible future.
Like many characters in the Archie Comics, King Acorn has varied alter egos in other dimensions. One version of him, Anti-Maximillian Acorn, also known as The Evil King, exists (but is never seen) on Anti-Mobius. This King Max was a complete despot, who was dethroned and cast into the Zone of Silence by his daughter Anti-Sally and her boyfriend Evil Sonic. Together they formed the Anti-Freedom Fighters and terrorized Anti-Mobius. Evil Sonic later mutated into a green hedgehog and reveals his real name as "Scourge the Hedgehog" and graduated to being a top-tier Sonic villain.
- King Acorn makes a cameo in the first episode of Sonic Underground. A statue of him is shown in the middle of the city.