A pork chop goes into a bar
A pork chop goes into a bar and orders a drink. The bartender says, "We don't serve food here."
This is another "walks into a bar" joke (though it doesn' use those words exactly), and also a pun. The joke here centers around the fact that in the phrase "serve food", food can be both the target of the service, and the thing being served. Normally, if someone said that they don't serve food, you would expect that they mean that they do not have food on their menu, but the pork chop is food, and also very obviously did not order food, but a drink.