Cross-selling, when two or more companies combine their promotional efforts, is the ultimate in character licensing.
As a marketing ploy it is at its most obvious in the fast food industry, where a toy of a character in the movie is "given away" as part of a meal promotion as the movie hits the screens.
It started in earnest in 1990 when Burger King and the Teenage Mutant Ninja Turtles were involved in cross promotion.
Not only was the film heavily promoted by the burger chain before it opened in the cinemas, but Burger King also featured in the movie.
In the decade since, it has become obvious which children's movie is due to be released or has just opened in the cinema by looking at the promotional products in the local McDonald's or Burger King.
McDonald's Corporation is in the middle of a 10-year global alliance deal with the Walt Disney Corporation.
Burger King Corporation has a similar deal with DreamWorks SKG - as well as a five-year deal with children's cable network Nickelodeon.
When Harry mania starts to die down it will be time for The Lord of the Rings hype to start up.
To find out if the movie is coming to a cinema near you, you could look in the newspaper - or take a look in your kiddie meal box. If there's a toy there, Bilbo Baggins is on his way.
