Acting differently in online games

[Haly]

It's relevant to other games but as I noticed it in WoW, figured I might as well focus on that.
I've been trying out a few different classes on a new server as some mates from my CS clan want me to join up with them again.
Played a Hunter for a bit (always end up playing hunters) and noticed, every time any one got in the way while I was trying to solo I kept thinking 'piss off'.
Next day, played a Druid (CS mate suggested they could do with a healer and I didn't want to go Priest) and suddenly I'm wandering round buffing players just because I can and because I like doing so.

Now, I've been a moody, over stressed git the past week so it might just be down to that. Just seemed weird and got me thinking a bit more analytically about what had changed.

So my question is:
Do you think playing a different class can affect how you interact with other players?
Do you take on the persona of what's expected of someone of that class?