You're travelling to another dimension

Think of the old 1950/1960's black and white 'Twilight Zone' TV show and what's the first thing that springs to mind? For most, after the spooky tinkling music, it's Rod Serling's introduction beginning 'Imagine if you will...', where he then describes various weird phenomena such as dimensions beyond space and time.

So, imagine if you will, the surprise of the many people who find out he never said that, and they are experiencing the Mandela Effect. Even though it's referenced in many places on the internet, not once did he say it in his introduction to an episode. This is the same class of Mandela Effect as Morpeus in The Matrix, where even though people can hear his distinctive voice in their head, he never said "what if I told you...".

It all started in the Twilight Zone

It's generally understood that a famous episode of The Twilight Zone from 1963 described the Mandela Effect phenomenon perfectly, even though it didn't used the phrase itself. The episode is titled "The Parallel" and featured an astronaut who returns from a mission to find some strange changes in his otherwise normal world. He seems to be the only one who remembers these changes, and has a hard time explaining them to those who don't see them. For example, the white picket fence outside his house has apparently been there all along, but he's sure he's never seen it before, Those experiencing the Mandela Effect today certainly know how that feels.

Wordplay

Another episode, but this time from a later incarnation of the series, has some uncanny similarities with the Mandela Effect. It's from 1985 and titled "wordplay". In it, a man slowly becomes aware of others using many ordinary words in the wrong way, for example everyone suddenly calls lunch a dinosaur. As the story moves on, this happens more and more until he realises it is he who is out of sync with the whole world, and has to effectively relearn many things he thought he was sure about.

Rod Serling/Rod Sterling

To make things even more interesting, Rod himself is the subject of a different Mandela Effect. Well, if your'e literally dealing with the show whose central tenet is to question everything, that's to be expected. This one is where many remember him as "Rod Sterling", whereas all references to him today are "Rod Serling".

This is a meme on the internet which is so prevalent it even has a dedicated generator.

Youtuber Maybe it's Mandela'd was the first to pick up on this:

Youtuber Moneybags73 covers it in more detail: