Getting to know your colleagues is important, so try not to alienate yourself. Don't feel you can't take part in office banter – providing it isn't gossip about your boss's personal life, chatting to your colleagues is a great part of team building.
Similarly, don't stay chained to your desk on a Friday night. If all your colleagues are going to the pub, join them. And don't forget to invite your boss – getting to know them better could be the first step in the right direction.