We've all had the experience of remembering things wrong. But how about when masses of people misremember things in exactly the same way?

It's called the Mandela effect, and essentially it's a false memory shared by many people who have a hard time believing their recollections are wrong even when presented with evidence to the contrary.

The phenomenon was named for one of the most compelling examples of collective mind trickery: the multitude of people who say they remember Nelson Mandela dying in prison in the 1980s, and even recall seeing clips of his funeral on TV. However, the South African anti-apartheid leader was freed from prison in 1990 after serving a 27-year sentence. He went on to become the nation's first black president in 1994, and he died in 2013 at the age of 95.

Another oft-cited mass delusion involves the Berenstain Bears children's books and TV series. A sizable chunk of the population remembers the spelling as Berenstein (with an "e") and is convinced it changed to Berenstain (with an "a") somewhere along the way. However, the name has always been spelled with an "a" ever since the first book debuted in 1962.

So what gives?

An abundance of theories

A paranormal consultant named Fiona Broome coined the term Mandela effect in 2010. She suggests the phenomenon might be caused by unintentional travel between parallel universes (the multiverse), each containing an alternative version of events and objects. In other words, in one universe it's Berenstain and in another it's Berenstein.

Some may dismiss this as pseudoscientific hokum, but according to Broome and others, if you remember Berenstein, your memory isn't flawed. Rather you're from the parallel reality where that spelling existed, which somehow merged with our current reality that spells it Berenstain.

parallel universes One theory about the Mandela effect is that particle physics experiments at CERN (European Organization for Nuclear Research) have pushed our world into an alternate reality. (Photo: Lee Davy/flickr)

Others speculate that the Mandela effect may be evidence of an equally unverifiable hypothesis in which trickster time travelers have somehow messed with the facts and flow of history.

Of course, scientists have their own explanations for mass misremembering. They blame it on imperfect human recall and unintentional memory distortions (called confabulations). Study after study has confirmed that memory is fallible, and false recollections are far more common than we realize. If you have any doubt, just listen to eyewitnesses in a courtroom offer wildly different versions of the same event.

What we remember, according to research, is often an interpretation of past events rather than a faithful recounting. Memories are influenced by our present expectations, thinking, emotional outlook and state of mind. That is, we often construct memories to fit what we currently believe, making up details and filling in holes with invented facts. Our memories also can be shaped and colored by what people around us think and remember.

Collective memory malfunctions

In fact, a lot of Mandela effect examples could be explained by common brain errors. For example, although memories of Nelson Mandela's death don't fit the facts, another South African anti-apartheid leader named Steve Biko did die in prison in 1977, and his funeral was depicted in a 1980s movie called "Cry Freedom," starring Denzel Washington. Are people simply mixing up the lives and deaths of these two similar men?

And how about another commonly held belief that the Monopoly mascot, Mr. Monopoly (originally known as Rich Uncle Pennybags), wears a monocle? He doesn't — and never did. However, an icon that resembles him, the top-hat-wearing Planters mascot, Mr. Peanut, does sport a monocle. Could this mass memory glitch just be a case of conflated images?

Or consider that many people falsely remember Kit Kat candy bars once having a hyphen in the name (as in Kit-Kat). There never was a hyphen, but could this be an example of multiple brains auto-correcting based on learned punctuation rules?

Kit Kat bars Kit Kat bars have been around since 1935, always without a hyphen. (Photo: Hazel Nicholson/flickr)

Are some Mandela effect mistakes simply memory mishaps that become culturally reinforced via social media and peers who misremember things in the same way? Or does the cosmos serve up different versions of reality?

Whatever theory you subscribe to, it could be a long time before we fully understand why so many people share the same memories of things that never were.

Here are more examples of Mandela effect mix-ups.

'Shazaam'

Entertainer Sinbad The entertainer Sinbad often appeared in genie-esque outfits during comedy routines, but he never starred in a movie titled 'Shazaam.' (Photo: Jerry Crawford (jcrawford3505)/Wikimedia Commons)

Remember that genie movie from the 1990s called "Shazaam" starring the comedian Sinbad as the genie? If you do, you're in good company. But your memory is incorrect. There's no such film, even though plenty of people swear they saw it. One explanation could be they're mistaking it for the time Sinbad hosted an afternoon of Sinbad the Sailor movies on TNT in 1994 wearing a genie-like outfit. Or perhaps they're thinking of another 1990s movie called "Kazaam" with Shaquille O'Neal in the genie role.

Star Wars: ‘The Empire Strikes Back'

"Luke, I am your father" is one of the most recognizable and iconic movie lines in history. Except that Darth Vader never said it. What he actually said was, "No, I am your father." It's hard to tell how this misquote became so pervasive, but perhaps over time people unconsciously began swapping out "no" for "Luke" to make the context clearer.

'Sex and the City'

Sex and the City A New York City billboard promoting the celebrated show in 2004 — and notice the 'and.' (Photo: torbakhopper/flickr)

Many people believe this popular TV series was called "Sex in the City." But the show always used an "and." No telling why so many fans remember it wrong, except that "in" maybe just rolls off the tongue easier than "and."

'Mister Rogers' Neighborhood'

A similar mis-memory involves the first line of Fred Rogers' intro jingle. Many people recall him singing, "It's a beautiful day in the neighborhood." However, the actual wording is, "It's a beautiful day in this neighborhood."

Froot Loops

Froot Loops The spelling of Froot Loops has remained the same throughout its 55-year history. (Photo: Mike Mozart/flickr)

More than a few cereal lovers swear this beloved childhood favorite was once spelled "Fruit Loops." But Kellogg's has always spelled it "Froot Loops" since the breakfast brand's debut in 1963. Do "Fruit Loops" exist in some parallel universe or is this simply another demonstration of the brain's auto spell-check function?

Snow White

"Mirror, mirror on the wall." People everywhere remember this famous incantation by the Wicked Queen in Disney's 1937 classic "Snow White and the Seven Dwarfs." Turns out what she really said is: "Magic mirror on the wall." The original Brothers Grimm story uses "Mirror, mirror," so a lot of young readers may have latched onto that version in childhood. Since then multiple "Mirror, mirror" references in popular culture have likely reinforced the mis-memory.

Jiffy peanut butter

Jif peanut butter Rolled out by Procter & Gamble in 1958, this peanut butter brand has always gone by Jif. Remember the tag line 'Choosy moms choose Jif'? (Photo: Mike Mozart/flickr)

As much as it might seem true, there's never been any peanut butter by this name. The real brand is Jif. Many people insist they recall the name changing at some point in their lives, but maybe they're simply confusing it with Skippy peanut butter or Jiffy Pop popcorn.