If the two women or the two men were a couple, they would not be confused as to who just got a car for Christmas.
The point is that they are both hoping their spouse bought it for them, with the implication being that the spouse who didn't is going to look bad by comparison.
Maybe dumb television commercials are a bit too advanced for you.
"It's somebody's favorite color...."
"Well 'somebody' has something to do in the garage!"
It is totally freeking obvious: a buggerer is buying a car for his buggeree!