Our refrigerator has a bad butter tray design. If you forget to lower the butter tray door and then close the refrigerator door, the butter tray door will get pinched between the refrigerator door and the refrigerator. If you close the refrigerator door too quickly, the butter tray door will crack.
This happened a few months ago, and I couldn't find the piece that broke off. But it still had enough of the hinge left on it to function. Today, I forgot to lower the tray door again and the whole corner snapped off, rendering it non-functional. This time, I was able to find the broken piece. I reattached it with Bondic, a liquid plastic welding material that cures in 4 seconds when exposed to the UV LED. It creates a strong bond, especially if you roughen the surfaces of the broken pieces with coarse sandpaper. The resulting blob of plastic doesn't look good, but it beats paying $(removed) to buy a new "dairy bin assembly."
This video shows you how to use Bondic and gives examples of what you can repair with it: