Ever wander why your work mate is all way's so childish some time's they could be missing there child or a kid that they are really found of. The character this person or so will show itself wile you are the witness of this expression event. Sometime's its not always good for the next person as you probably where really serious wile this person came and went on being selfishly childish and that really irritates because this person in turn influences you to be the same way and that could disrupt the productivity of the company but it could also be healthy for mentality sometime people react this why without knowing that's why things go wrong but if you know then you can go ahead and classify this as having fun.
The truth of the matter of immaturity is children is the source and most probably you just miss being a child and immaturity is how you express your inner childish desire's. It tend to get really dangerous in the teen ager's as this tends to develop into a illness that need one to fit into a certain group of people that you probably feel less worth full to, it's called "peer pressure" and some do anything to fit in sometimes if you don't fit in they call you gay.
Sometimes in life you just have to relax and wait a second before you get to doing a few stuff but no one told anyone how long they where going to live and any this all is just happening so do it your way.