It's a joke. The books are called The Berenstain Bears. Because surnames ending in -stain are extremely rare and surnames ending in -stein are fairly common, a lot of people misremember them as The Berenstein Bears.
This has spawned numerous conspiracy theories about the name changing. There is a group of people who seriously believe they've somehow travelled into a parallel universe where the only difference is that a children's book series is named differently. This theory is often referred to as "the Mandela Effect", which is named after how a lot of people mistakenly remember hearing about Nelson Mandela dying years before he actually did (and yes, these people claim that they've accidentally travelled to a parallel universe where the only difference is that Nelson Mandela lived another 15 years). The theory sounds like a joke, but its proponents take it dead seriously, and they've been known to start flamewars over it.
As such, a lot of people like to make fun of these conspiracy theories by concocting the most ludicrous theories we can think of.
This has spawned numerous conspiracy theories about the name changing. There is a group of people who seriously believe they've somehow travelled into a parallel universe where the only difference is that a children's book series is named differently. This theory is often referred to as "the Mandela Effect", which is named after how a lot of people mistakenly remember hearing about Nelson Mandela dying years before he actually did (and yes, these people claim that they've accidentally travelled to a parallel universe where the only difference is that Nelson Mandela lived another 15 years). The theory sounds like a joke, but its proponents take it dead seriously, and they've been known to start flamewars over it.
As such, a lot of people like to make fun of these conspiracy theories by concocting the most ludicrous theories we can think of.