For the sake of getting all angles looked at, the mess could have been made easily by uu just playing Sburb as the sever player. Rose made a rather big mess of Johns house, for instance.
Also there is the fact they have different blood.
IDE: Something I thought of a while ago, UU is the hero of space. She goes though the game with uu, and after a while something happens and she flips her shit, starts identifying as male, and gaining time powers. He then goes back in time as uu to complete time loops, although this time as the hero of time. That is one reason that uu is so damn frustrated by all the shenanigans, not only are they stupid but he has already had to deal with them once.
Edit: this still doesn't explain the blood. I suppose he could have gotten so sort of transplant? Or he could be lying about it for some reason. Or this could be a bullshit crack theory...

















Giant robots in the last days of man.









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