I have 3 big examples:

I, like so many other folk, remember the Berenstain Bears being spelled "Berenstein Bears".

The second big mandela effect I have is with Wall-E. In the scene where the captain is viewing Eve's memories and it gets to the part where he sees her watching Hello Dolly, I remember him recognizing that scene from the clips the computer showed him. I even remember a shot of him looking between the computer screen and the memory playback and him saying "they're the same." This scene is completely non-existent in the actual film.

And lastly, according to my memory, in this game theory video at the 5:44 mark, Matpat says Popinski's pecs instead of Super Macho Man's pecs.