It could only happen in a tavern game
We're playing free poker for bar tabs, and drinking for 4 hours to make the final table, so strange things happen.
Final three, all drunk, games been going way longer than usual and kareoke is already going. Six drunk guys in cowboy hats are singing "Low Places". I have small stack and get AT suited on the SB. The guy on my right shoves a bunch of chips in the pot, and I think he's all in, but he's actually slouched over another pile of chips equal to what he pushed. The BB has an immense stack, and he goes in the tank when I shove. So me and the other guy are looking at each other, half drunk and half asleep and he shows me his cards. He has 88. I think he's all-in, and I show him my cards. The BB notices this, but says nothing. He just goes farther in the tank. Eventually he flat calls.
I then realize there is still action between them two. So I flip my cards up; since I showed one, I have to show both. The BB then shows me his AK. I'm third best and dominated, only card that will help me is a ten. 88 is best, and looking good because the aces burned each other's outs. The door card is an ace, making the AK a big favorite. The flop is ATx, making me a big favorite.
But the BB is looking at all those chips, and 3 outs times two, and he decides to try and make a side pot. The 88 folds. River is an 8. Now he's apopleptic. If he didn't show me his cards, none of this would have gone down. He hung himself with his own thoughtless play, and he knew it. Then the river comes an A, giving me AAA88 to his 888AA, and he would have lost anyways, so the show and the fold worked out well for him.