I got my quarterly haircut the other day. A neighbor remarked, "I see you got a haircut," to which I responded with the old joke, "I got 'em all cut."
In this as in so many other cases the humor derives from ambiguity, in this case amphiboly (syntactic ambiguity.) The spoken 'I see you got a haircut' can be heard as 'I see you got a hair cut.'
The neighbor laughed at the joke, but I spared him the analysis, not to mention my theory of humor, both of which would have bored him.
Two relevant maxims: 'Tailor your discourse to your audience' and 'Among regular guys be a regular guy.' And a meta-maxim: 'Step out of your house only with maxims at the ready.'