Why are my ice cubes such weirdos?

I use a lot of ice. An embarassing amount really so I have a lot of ice trays in the freezer at any given time. Occasionally, I’ll open up the fridge and one or two cubes has what looks like an icy spike of doom coming out of it. I thought for a second maybe the fan in the freezer might have caused it but if that was case there would be more cubes with the same spike. And there really isn’t that much movement in the freezer anyway. It isn’t my freezer because it’s happened in two separate refrigerators now that I’ve noticed. So, what’s up?