It was right there, all along.

[Sibyl]

Have you ever studied something so much or for so long that you just can't fathom that you've missed any details?

The subject matter does not matter for this discussion, but it just happened to me this morning while staring at DVD caps of TMP while working on my Refit Enterprise bridge chairs. A particular detail jumped out at me from Uhura's chair that I'd never noticed before. It's on all of the chairs, but I noticed it with Uhura's at this time.

 

[Timewalker]

I play a lot of Hidden Objects games, and there are times when I swear that something the list says is there really isn't, because I've scoured the picture up, down, and sideways over a half-dozen times.

Then I use the "hint" button and there it is.

 

[Mr. Laser Beam]

It wasn't until years after TNG aired that I realized: Betazoid eyes (like Deanna and Lwaxana) are all black.