Sometimes, sometimes the kid sees the commercial and just annoys the hell out of their parent until they buy it; specially in Christmas because is socially expected.
This reminds me of an example in a book I read about advertising. Toy companies increase advertisement before Christmas but lower production rates so the big toys of the season sell out. The reasoning is that kids bother their parents to buy the toy and the parents promise they will but can't since its all sold out so they buy something else. The toy companies cut the ads a little before Xmas only to ramp it up again a month or so later at which point the kids complain that you promised and parents psycologically feel obligated to buy. The toy companies then get 2 purchases from you. They use your kids against you