Plus Galvatron considered himself to be a separate character from Megatron in the movie, even though he was created from him.
I'm not sure about that. In Galvatron's first interaction with Starscream, he boldly strolls into Decepticon HQ, and casually insults Starscream. That was enough to make Starscream ask "Megatron? Is that you?" Galvatron says "Here's a hint" and kills him. Now the question is, is that a hint that he
is Megatron, and that he's really pissed off at Starscream's latest assassination attempt, or is it a hint that he's
not Megatron anymore, in so far as he's willing to kill Starscream over assassination attempts? We must also consider how inexpensive death has suddenly become in this world once the movie started. Or is there some other answer?
Of course, then Rumble avoids the puzzle by asking "What did he say his name was again?" Galvatron says "Galvatron", so that's what everyone calls him, because they don't want to die. But it's never made clear to the Decepticons what Galvatron's stance is on the "Megatron" thing.
And then when Galvatron faces Hot Rod, Galvatron says that he killed both Optimus Prime and Ultra Magnus. I think that says that Megatron and Galvatron were both the same character. Galvatron is Megatron with a new name, and a new form. Megatron didn't die in the creation of Galvatron.
IIRC, in season 3, Galvatron was afflicted with insanity in the first episode, and when they eventually tried to cure him of it, they said that he might revert to Megatron (who was still inside Galvatron), at which point Galvatron started resisting and screaming that becoming Megatron again meant death for him as Galvatron. That could be attributed to his insanity, or to character change from movie-to-season due to writer changes. Or maybe it was true, and being Galvatron means being the sum of his entire past, and reverting would mean losing something that had become vitally important to him.
