It would seem that what is currently commonly known as commercial property development in comics (i.e. creation of a comic for a different reason than basically telling a story, but rather to sell stuff or prepare for a movie deal) is not as new as you might think.
The Smurfs, arguably one of the most valuable comic “properties” in the Franco-Belgian tradition, originally saw the light as (yet more) comic relief in La Flûte à six schtroumpfs, the sixth album in Peyo’s series Johan et Pirlouit. Their first proper adventure though, Les Schtroumpfs Noirs, was as the first in Spirou famed mini-récits, a series of inserts in the magazine that, after some tinkering, could be made into a tiny book with a full fledged story.
The eleventh story with the little blue dwarves, however, has an even more interesting background. The book was initially created as a promotional publication for the French biscuit bakery Bisquiterie Nantaise in 1967. It was only included in the main series in 1970, after serialisation in Spirou magazine in 1969 (starting, quite befittingly, in the Space Special issue, coinciding with the moon landing). Or, never hesitate to repurpose your creations.
(ad from Pilote Magazine #396, 1967)