Fiona Broome, a paranormal enthusiast, was certain she had heard that Nelson Mandela had died in the 1980's (while in prison) when in reality, Nelson Mandela died in 2013. Instead of just admitting the mistake and that being the end of it, Fiona Broome asked other people if they thought Nelson Mandela had died in prison too. She found several people that did. Instead of attributing this to misinformation that had spread around, possibly the result of a misunderstanding, Broome concluded that the phenomenon was caused by something completely different: parallel universes.
While the concept of parallel universes isn't new, Broome may be the first person to go so far to avoid admitting she was wrong. She theorized that people freely and unknowingly move between parallel universes that may be completely identical except for a few minor changes. In her case, Broome posits that she was once in a parallel universe where Nelson Mandela did die and prison and she learned that face while in that universe. She then entered this universe without knowing it or having her knowledge of Nelson Mandela being affected. This is the Mandela Effect.
Since Fiona Broome first discussed this idea on the internet, many people have come forward to give evidence of its possible validity. This evidence includes the misremembering of brand names such as Febreze and Looney Tunes. It also includes a large portion of people that claim that Berenstain Bears is actually spelled "Berenstein Bears." However, it seems much more likely that people just don't want to admit that they were wrong.
Take, for example, the Berenstain Bears situation. As a child, someone is read the Berenstain Bears books by their parents. Like many children, they don't take any notice for how Berenstain is spelled. This child then grows up and takes more notice in how things are spelled. They notice the names Stein, Goldstein, Rubenstein and other -stein names. They develop in their mind that Stein should be spelled s-t-e-i-n (regardless of whether it is pronouced with an "e" sound or an "i" sound.) Now this child is online and sees that Berenstain Bears is spelled with an "a." "But that can't be right," they think, "It has always been an "e." The child goes back and finds one of the books, it is spelled with an "a." Naturally, they jump to the only logical conclusion, I must be from an alternate reality where Berenstain is spelled with an "e." For there is no possible way that they could be wrong. Then again, how could we know we haven't changed universes?
