Sorry but by my recollection, it was always spelled JC Penney and I never heard that Mandela died in prison in the 1980s and the peanut butter was always spelled "Jif" and the WB cartoons were always "Looney Tunes" (not Toons) and the TV show was always "Sex AND the City."
The spelling of words and odd wordings in general are just things I've always noticed. For example, it has always bugged me that the "R" in Toys R Us is always written backwards in their logo. It seemed like a mean thing to do to kids who were learning to read.
I don't know about the other alleged "Mandela Effects" because I never paid much attention to them but, judging by the ones I'm familiar with, I am skeptical of all of them.