By Joia Shillingford
BBC News business reporter
The Star Wars franchise has generated an estimated $20bn (£10.8bn) in revenue to date.
Star Wars fans were out in force for the Hollywood opening of the film
But the latest film, Star Wars Episode III: Revenge of the Sith, could be the biggest moneymaker of them all.
Not just from bums on seats in the cinema when it opens on Thursday 19 May, but from special promotions.
This darker, deeper Star Wars - which shows how Luke Skywalker's father goes over to the dark side - could have consumers cheerfully parting with cash.
In one US cinema, it is playing on 10 screens and trade newsletter Weekend Box Office estimates that US cinema sales could soar past $300m towards $400m.
The biggest beneficiary is set to be Star Wars' director George Lucas, who lucked out when 20th Century Fox let him keep the ownership of the merchandising and sequel rights to the very first Star Wars film.
The five Star Wars films before Revenge of the Sith generated $5.7bn in cinema and DVD sales, and $9bn in merchandising as well as marketing revenues from corporate sponsors.
Mr Lucas' licensing arm expects Revenge of the Sith to make between $1.2bn (the figure for Episode II: Attack of the Clones) and $2bn (Episode I: The Phantom Menace).
The first Star Wars film created today's, some would say mercenary, approach to milking extra money from films through selling toys and computer games based on the film's characters.
The opening weekend of Episode III is expected to gross $147m
"The advent of Star Wars in 1977 really marked the birth of the modern movie licensing and merchandising business," says Marty Brochstein, executive editor of The Licensing Letter, a trade publication for the licensing industry.
This time - possibly because this is meant to be the last Star Wars film in the series - the marketing hype is much more intense.
The latest Star Wars film has more promotional partners than virtually any other film, from Burger King to mobile phone company Orange.
Pepsi, M&Ms, phone company Cingular, and convenience-store chain 7-11 have all linked themselves to the film.
Darth Vader, who can be seen chatting to talking M&Ms in an advert, also stars in several promotions.
These constant reminders of the film could help get cinemagoers out in force, though some will resist as the marketing hype gets too much.
Toys are the biggest merchandising category, prompting Toys R Us to open the doors of 316 of its US stores and 21 international branches at one minute past midnight.
Some fans like to embrace their dark side as Darth Vader
Hasbro, which makes the most Star Wars toys, is also hoping for sales success.
And there will be nine Episode III games from Lego, the Danish toy building brick company.
Some of the people who bought Star Wars figures and light sabres for the very first film are still collecting them.
Stores hope to cash in on the cult status of Star Wars memorabilia to sell even more.
"Star Wars has a rabid fan base, including collectors who want to complete their sets," says Anita Frazier, entertainment industry analyst at US research firm NPD.
"Sales of Star Wars toys were up 30% in the first quarter, from last year's first quarter, even though most of the latest toys weren't out till March."
Other films could benefit from their association with the latest Star Wars movie too.
Firms want the trailer of their next film to be shown at Revenge of the Sith screenings.
That gets them a big audience for the trailer and, hopefully, a big audience for their own film.
Sony even wants to show a trailer for the film of religion-and-art bestseller the Da Vinci Code, which won't come out until next year.
George Lucas is said to have limited the number of trailers that can be shown to five but distributors are now trying to make their trailers shorter so more can be shown.
Bums on seats
So cinema revenue from Star Wars is a relatively unimportant part of the mix then? Not exactly.
Cinemas too are hoping the film will boost their fortunes.
In the US, film attendances have fallen 7% and the film will be an opportunity to boost sales of drinks and popcorn.
Advance booking has been powering ahead and some cinemas are showing the film around the clock, with a much larger-than-usual 18,700 copies in circulation worldwide - over half in North America.
These takings could come at a cost to other businesses, though.
Recruitment firm Challenger, Gray and Christmas estimates that US businesses will lose $627m through staff taking time off sick to be among the first to see it.
Not surprisingly, the black market wants a cut of the Star Wars magic.
Pirate DVDs should be on the streets of Beijing in China in hours, though releasing the film worldwide on the same day was designed to cool counterfeiting fever.