My favorite is Mr. Burns answering the phone "ahoy-hoy".
It's funny on so many levels, and it requires an amazingly esoteric bit of knowledge in a time before it was easy to find that kind of stuff on the internet.
"Alexander Graham Bell originally suggested 'ahoy' be adopted as the standard greeting when answering a telephone, before 'hello' (suggested by Thomas Edison) became common." - from the Wikipedia page on 'Ahoy'.
When the joke was first made (Mr. Burns using the phrase), it wasn't "common" knowledge, but it was a known thing. Like one of the "fun facts" you'd find on a cereal box, or in between segments of a TV show, or as a Jeopardy question.
I remember seeing the episode and understanding the joke... it was just meant to make Mr. Burns appear *really* old.
Maybe I just had a ton of useless/esoteric knowledge as a kid -- that's likely too.
It's funny on so many levels, and it requires an amazingly esoteric bit of knowledge in a time before it was easy to find that kind of stuff on the internet.