"Incoming Weasel!"

A friend of mine, I'll call her WordGirl, used it in one of her many stories of the adventures of her only-begotten son and her. The two were in a department store and the son needed tube socks. While looking at the assortment, he found a pair of designer socks that had the logo of their town's baseball home team. He wanted his mother to have a closer look. So, he grabbed the socks, called out his mother's name, "Hey, Mom!" and when she turned around to him he threw them at her and shouted, "Incoming weasel!"
Now you want to know where that comes from and why it's so funny.
Well, the mother and son duo were big (nay, HUGE) fans of The Addams Family. They knew all the lines of all the episodes. They could both imitate Lurch's, "You rang?"
In an animated episode of the Hanna-Barbera Addams Family series, Uncle Fester has a scene in which he shoots weasels from a cannon. As they are fired through the barrel, Fester shouts, "Incoming weasel!"
It was one of those private jokes between mother and son...