I think we all are different around different people - we'd better be, because that's, like, sane and stuff.
to a degree, that should be the case.
work behavior vs. how we act at home, for example -- like, nobody at work needs to see me in pjs and glasses, sprawled out on a couch reading. and talking in my most professional tone to friends/family would just make them wonder if I'd gone off the deeper end.
that said, there's nothing I do that isn't still part of me. no putting on a persona that doesn't fit into the whole -- there are some people who are not that way. and especially awful, to me anyway, are those who excuse away poor behavior by saying whatever persona is a put-on -- no, you're just a jerk.