Stuff and Moonshine

I'm pretty sure the main joke is just the feeble "wrong" instead of "left" substitution. However there is often another intended meta-joke in that the joke is so feeble that it's funny that there's this simpleton trying to be funny. Sort of like Inspector Clouseau or the Three Stooges only clumsy in their joke telling instead of physically clumsy. This was the intention behind a lot of what Johnny Carson did (eg. Carnac the Great), and almost everything Red Skelton did. Red described it as "having fun" as opposed to "being funny" in that he was sardonically laughing at himself and the awfulness of his act and inviting you to laugh along with him.

Personally I find it too artsy-fartsy and high-falutiing kind of comedy that's only popular amongst comedians; rather like noodling Jazz music is mostly enjoyed by Jazz musicians.

BTW - Mad Magazine did the directional joke better in a Dave Berg nautical feature.

How to tell port from starboard: There are two directions. "Port" has the same number of letters as "left". So "port" is left. Now the other direction must be the nautical term that remains and we see that "starboard" is left. Simple!