My own headcanon Galvatron that has now turned into it's own AU/'verse known as the Extriverse.

Facts/Notes about this Galvatron (Both canon-Galvatron info and headcanons ahoy):

• Galvatron and his cohorts spent a week inside Unicron mutating into their current selves, upon which they hatched from fluid-filled chrysalises in their current state and left Unicrons body to enact his will.
• He’s bio-organic and functions differently enough from regular Cybertronians to be at the very least considered a sub-species.
• The battle with Galvatron and Unicron lasted for two years. Unicron himself only showed up nearer the end.
• Galvatron suffered a lot of torment from Unicron for so much as even considering doing things Unicron did not want.
• During the latter part of the war with Unicron Galvatron did what he could to help in the take down but in the end was forced to comply with Unicrons commands.
• Inside Unicron Galvatron tried to open the Matrix to kill or incapacitate Unicron. The Matrix opened slightly for him. It sensed the genuine desire to be free and defeat Unicron and responded to that but sensed Unicron still infested his mind so it did not.
• Galvatron could’ve done something/more to prevent Hot Rod from getting the Matrix but used his last bit of energy to control himself, letting the Autobot take it, even though he likely would’ve got it anyway.
• Is full of chaos energy.
• He spent a full year in the plasma baths of Thrull.
• Said plasma seeped into his cranial chamber and caused a slew of problems for him:
• He suffers from occasional severe failures in reality processing, leaves him on the bring of a perceptual crash most of the time, A Malignant Plasma-neural tick, His metaprocessing circuitry is brittle, Often these ‘attacks’ or ‘moments’ cause him to have things similar to hallucinations often perceiving his own allies as enemies prompting him to attack them. Occasionally it causes him to have muscle spasms.
• Galvatron is however smart enough to be aware of these and attempts to ‘compensate’ for his behaviour by being awkwardly helpful and overprotective of them.
• He fears himself due to these ‘breakdowns’.
• Due to his strange/different perceptual range Galvatron picks up things differently or notices things others can’t, it can be both confusing for him as much as it can be a bonus.
• Being aware of his own issues and how some of the more aggressive/less-forgiving ‘cons view him leaves him with severe self-image/self-esteem/self-confidence issues.
• Galvatron, like Cyclonus Scourge and the Sweeps, has a “Garbage Gut”.
• While Unicron was alive Galvatron and his cohorts had seemingly unlimited strength and power, now he’s “"dead”” their power is noticeably weaker but they are still forces to be reckoned with.
• Like other Unicronians he can make his optics appear to be ‘aflame’, this is purely an aesthetic effect.
• Gets adopted by Soundwave
• Due to being a “perfect” form of the Quintessons TransOrganic experiments the Quintessons both view Galvatron as a severe issue yet an invaluable test subject.
• The incident on Torkulon left Galvatron and Cyclonus with a considerable strain on their relationship. Cyclonus felt guilty while Galvatron struggled to trust him again feeling hurt at the ‘betrayal’.
• Rubs his cannon as a kind of ‘stimming’ and likes having something to fiddle with.
• His stomach and thighs are soft and ‘squishy’ but don’t be fooled. They can still pulverise.
• Rubbing his stomach calms him down quickly and as such he likes it but only Cyclonus is allowed to do such.
• He can purr and does ‘blep’ when content. Tail wiggles sometimes too.
• His hand-pads feel like smooth leather.
• Occasionally has nightmares about Unicron.
• Always frees slaves.
• Referring to him as Megatron or referencing a life before his current-self makes him feel incredibly uneasy.
• To transform his arm folds up and the ‘wing’ stretches out from his elbow, arm and body.
• His cannon only ‘moves’ like a head while he’s transformed, otherwise it remains static.
• Is bizarrely fond of children and refuses to do anything dangerous near or around them. Making Daniels fear of him somewhat ironic as Galvatron would be unable to hurt him.
• Has an incredibly ‘close bond’ to Cyclonus in particular and shares a room with him.
• Has rough nights of sleep and doesn’t get as much rest as he should. This often leads him to sleep in various places, unsurprisingly he can be found asleep with some Sweeps in a pile.
• Is afraid of leeches due to the incident with the Dweller that almost cost Cyclonus his life.
• Can go days without eating unless someone reminds him to.
• Thinks and processes things in weird ways and gets distracted somewhat often but it doesn’t always mean he’s forgotten what the original idea/plot was.
• Mockingly calls Ultra Magnus “Shoulderstacks” instead of his actual name and occasionally does it to others to be cheeky.
• Calls Hot Rod/Rodimus Prime "Runt" however he actually never meant it in a cruel way and holds some respect for the youngster. After all he did defeat Unicron and free him from his abusers grasp.