This one probably differed the most from the original tale, and I wasn't expecting basically anything after the first ten minutes.

I didn't know what to expect, but I was surprised just about everywhere. Not to mention I watched it without seeing any trailers, reviews, or books. I didn't see any of it coming, except the Naveen and Tiana relationship.

or Tangled.

I don't think anyone expects when they first start watching that Pocahontas and John Smith aren't going to end up together...
also Princess and the Frog for the reasons listed above.

And Tangled

The ending surprised me a lot.

And Princess and the Frog

I didn't really know what was going to happen, tbh.