Retcon effect

The Retcon effect (retroactive continuity), popularly known as the Mandela effect, is a feeling of alienation produced when an individual's memory conflicts with the inter-subjective shared memory of others or physical evidence that their memory is false. In some cases, this alienation is taken as evidence that the experiencer of the effect has their origins in an alternate reality where events occurred in such a way that their memories are correct and any conflicting memories of others or physical evidence contradicting their own memories simply represents events that have occurred differently in their present reality, and that the experiencer has therefore been transported (or shifted) by some means into their present reality; or, in other interpretations, that there has always been a singular, shared reality, often supposed to be virtual in nature, but it has been modified by unknown agents, and these agents have altered the memories of those whose memories conflict with the experiencer's own and replaced (or transformed) the physical evidence to conform to the modifications, but left the experiencer's own memories unaffected and have potentially left other evidence (or residues) of the original reality.

The identification of the effect as the Mandela effect was made by Fiona Broome, and is so-named for an atypical memory of Nelson Mandela, a South African anti-apartheid revolutionary, being killed during the 1980s, as opposed to the typical memory of his spending the 1980s in prison, being released in 1990, and becoming president of the Republic of South Africa in 1994.

Other popular atypical memories that are referenced in connection with the effect include:
 * a children's book series called the Berenstein Bears, as opposed to the Berenstain Bears;
 * a family film called Shazaam starring comedian Sinbad as a genie, as opposed to (or co-existing alongside) a family film called Kazaam, starring basketball player Shaquille O'Neal as a genie;
 * the character Rich Uncle Pennybags, mascot of the board game Monopoly, wearing a monocle.

Resources

 * &mdash; "a place to discuss the effect under the presupposition that for whatever reason, *it is really happening,* at the exclusion of the theory of Confabulation."