A circular coin held at a slant to you doesn't look like a true ellipse. The half that's closer to you will be fuller and the half that's away from you will be flatter because of perspective.

ETA: Pfft points out below that circles actually map to ellipses under perspective projection. Before I posted this, I took a look at an angled circle, and it looked as I described it-- at the moment, they're looking like true ellipses.

Speaking of the yellow banana, people do a lot of filling in with color. Take a careful look at someone who's wearing a monochrome garment. Very little of it will be the color you think it is-- most of it will be much lighter or much darker, and this doesn't take into account the effects of the colors of nearby objects getting reflected onto it.

It took a major effort of will for me to hear the way I pronounce water. I have a Delaware accent, and I say warter. It looks ugly in print, but it sounds wetter and altogether more like H2O than the more usual wahter-- which also looks weird in print.

My last name is Lebovitz. Most of the people I've dealt with can't say it accurately or remember it, even if they're told it twice, had it spelled for them, and shown it in print. The problem is that Leibowitz is more common, and most people seem to slot in the more common name so strongly that they can't perceive immediate sensory input that's a little different.

This is an irritant for me, but the cognitively important aspect is that if something so simple (all the phonemes in my name are part of the standard English set) and objective is so hard to perceive, how much more are we missing which doesn't have a person saying "that's a short 'e' and a 'v' not a 'w' " to us?