BERENSTAIN or BERENSTEIN? I remember it as the latter, but it’s 100% the former. This is something called the Mandela Effect, which, sez Wikipedia is:
False memories can sometimes be shared by multiple people. In 2010, this was dubbed the "Mandela Effect" by self-described "paranormal consultant" Fiona Broome, in reference to a false memory she reported of the death of South African leader Nelson Mandela in the 1980s (who was at the time still alive), which she claimed was shared by "perhaps thousands" of other people. Other such examples include memories of the Berenstain Bears' name previously being spelled as Berenstein.
I’m still spelling it -stein