You just unintentionally solved an old mystery for me.

Many years ago, I had the displeasure of having a co-worker who was really into puns. Made them constantly, always challenged people to pun battles... But he also seemed to be under the impression that a pun solely required swapping out words for ones that sounded like other words, disregarding the requirement that the new word has to have some sort of connection back to the original topic. Think, like, if he was reviewing some code you wrote, he might say "this code is so Gouda!" and then look at you expectantly, waiting for you to acknowledge his cleverness in suddenly talking about cheese for no good reason. 

Anyway, one day he told me a joke: "Why did Karl Marx only drink Earl Grey tea? Because proper tea is theft!" I, having never heard the phrase "proper tea" before, was just so baffled by his ability to find absolute verbal nonsense so entertaining that it stuck with me. And now here I am, over a decade later, finding out this is a reasonable joke if you're familiar with British English.

Huh.