Domo Arigato, Mr. Roboto

This one is from the mind of Jill, thanks for the help. So why is it that when we get tables that are groups of Japanese men, we find the need to bow? I understand it is customary to bow in a greeting or departure or even as a thank you, but since when did I become an Asian man? Is there something in the air around their table that makes me do it? Hell, I don't bow to anyone else, yet here I am picking up that empty pint glass off the table and the man decides to hand it to me, so as I grab it, I bow! Now what do they think? Do they think I'm a jackass or do they think I'm doing it to be nice, did they even notice I did it? Quite similarly, what about when I get a table with an accent, and now I speak to them with an accent, really, what happened, did I get a case of stupid for just this table?