The Mandela Effect is a theory put forth by writer and “paranormal consultant” Fiona Broome that shared false memories are in fact glimpses into parallel worlds with different timelines.

Broome says that the origin of her theory came out of a discussion about whether or not Nelson Mandela died in prison. Naturally, this happened backstage at Dragon*Con.

Many people who believe in the theory insist that the popular children’s book series The Berenstain Bears was once known as The Berenstein Bears.

And that there are either 51 or 52 states in the United States, not 50.

Most of the people who believe this happen to be from other countries around the world.

Or that Scotland and Wales were once much smaller than they are today, and that Wales bordered Scotland on the east.

Others insist that they have memories of New Zealand, Australia, Sri Lanka, Honduras, and other places being at different places on the globe.

Some say they remember Hurricane Katrina hitting New Orleans in April 2005 rather than August 2005.

Which doesn’t really make sense if you know anything about hurricanes, but hey, maybe weather just works very differently on parallel earths.

Some recall that the Columbine massacre happened in 1996, not 1999.

People have some pretty vivid “memories” of him getting crushed by a tank, though.

A bunch of people remember there being a different Disney World in the Orlando region that was used as a beta test for the real park.

Some have memories of Patrick Swayze making a full recovery from cancer rather than dying in 2009.

Some swear that Muhammed Ali died, though he’s still with us.

Broome herself insists that she remembers Billy Graham’s funeral being televised simultaneously on many networks around 2009, though he’s still alive today.

Some people believe Neil Armstrong died a year before he actually did in 2013, and that he made a reference to someone named “Mr. Gorsky” while on his voyage to the moon.

Some people remember Dr. Martin Luther King Jr. being killed with a handgun at close range, rather than a rifle from a distance.

Some believe that the word dilemma used to be spelled with an N.

And that there is another world where it is correct to spell definitely with an A.

And another where it’s OK to spell Parmesan with an E.

They also think that pronunciation shifts — or people learning how to pronounce a word correctly — is evidence of an incursion from another timeline.

Some believers in the Mandela Effect remember things that are extremely specific to their own lives.

Like, really, really, really specific memories.

People say they remember all kinds of odd moments in entertainment, such as the character Chakotay being killed off in an episode of Star Trek: Voyager only to come back with no explanation a few episodes later.

Broome says she asked Robert Beltran, the actor who played the role, about it, and he told her that a story involving his character’s death was never written or filmed.

Some insist that the show Ghost Hunters was called TAPS.

TAPS is the name of the stars’ investigative group, The Atlantic Paranormal Society.

And apparently there’s another timeline where Katy Perry is known as… KATE PERRY.