Don't call unless someone is dead or the house is on fire ...
Back in the day, say around the 50s, kids weren’t allowed to call their parents for anything other than an emergency—and an extreme one at that. Any small stuff (like tattling on a sibling) had to be figured out on their own. Parents would reiterate that to their children by saying, don’t call unless someone is dead or the house is on fire. Today, the phrase is pretty meaningless thanks to kids having their own phones to text their parents whenever, and the parents don’t seem to mind much either as many homes preach communication as the key to a healthy family.