You know, you have to be very careful about this.
I worked on a show once where there was a general sense of frivolity among the cast and crew, with little jokes happening throughout the show - the show was silly, light and airy - and actually helped the morale and the general nature of the show. As things happened, I pulled people aside and said that it CAN NOT effect the show, but I hope they could figure out a way to have fun and do the show as directed, not have the audience or me know, and do their little jokes, so be it. Life went on, everyone had fun.
I had to leave the show, and my assistant had to take over. She had VERY little tolerance to this type of behavior, and came down hard. Did the joking stop? No, it actually escalated. Stage Manager came down harder, they responded more. It did eventually bleed out and effect the show.
It's a fine line to walk.