The film, starring Macaulay Culkin as young Kevin, is a popular festive favourite with millions, but still new details about it are coming out.
In one scene, Kevin is seen finding a picture of mean brother Buzz’s girlfriend, and says: “Buzz, your girlfriend… WOOF!”
The intended comedy comes from the fact that the girl in the frame is made to look especially goofy – but it’s not as mean-spirited as you might think.
According to the actor who played Buzz, movie bosses knew it would be unkind to cast someone as the girlfriend, just for their appearance to be mocked.
And so they got the art director’s son to dress up for it instead.
“[They] decided it would be unkind to put a girl in that role of just being funny-looking,” Devin Ratray told Yahoo.
“The art director had a son who was more than willing to volunteer for the part.
“I think if he had known it would become the highest-grossing family comedy of all time, he might have had second thoughts about it.”