I've seen this posted around other forums and reddit, but did a couple of searches here and didn't see it listed. If you have eggs in a plugged in fridge, the eggs won't hatch. They'll keep incubating, but they'll hit 100% and stop.
Load the game, everything hatches. If I then close and reopen the game without saving in the middle, I can watch them all hatch each time I load the game.
Put eggs in a fridge, wait for them to hit 100%, reload game, and pop goes all the critters