The Mandela Effect happens when a large group of people believe something to be true that never happened. The phenomenon gets its name from Nelson Mandela. A large number of people remember Nelson Mandela dying in prison in 2009. However, he did not die until 2013. Another example that rocked my childhood memory is the popular children's book, "The BerenstAin Bears." I, along with many other people who grew up reading these books, vividly remember the title as "The BerenstEin Bears." There are countless examples of this effect. Just YouTube "Mandela Effect" if you ever want to waste a good part of your day. There are theories that this effect is proof of parallel universes.
I moved to Portland in August, 2011, and lived in apartments on 21st and Belmont. I frequented the park on the corner of 20th & Belmont. The park I remember as "Colonel SumNers Park." After a heated debate over the name of this park, I looked it up. It's "Colonel SumMers Park." I have since taken a poll among many of my Portland friends. Some of which have moved here recently and some who have lived here many years. I have consistently found their memory of this park's name to be consistent with when they moved here! There seems to be a change around 2013. People who have known of the park before then remember it as "SumNers," after "SumMers."
I have even found several articles from The Portland Mercury referencing "SumNers Park." What's the deal!? Has Portland transitioned into a parallel universe?