I know that there used to be a way to do it, but I believe 1.69 fixed that. Well, until someone figures out a new method I guess.
But, you way want to consider the legal implications of writing information to other people's hard drives without their knowledge or consent. Also, since you'd most likely have to use some type of third party program, it creates a potential risk to your own computer.
I don't really see the point anyway since the host can replace your character, delete it, or simply ban you.
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