a series where there is a dominant media in the series with bits an pieces of other types of media that may not be as well advertised but still are considered canon to said series. example:so you've got a movie trilogy, but there's a character in the second film who apparently at some point or another met the protagonist before. Its tradition in a jigsaw series for there to be some minor piece of branch off merchandise like say a comic book or a video game that will still take place within the canon of the series and explain how they know that person.
having a series that continues in this direction will have prequels, in between-quals and generally becomes fodder for someone to be considered a geek if they know any interesting facts about the series beyond just the three films in said example.
however it is still possible for everything to be released in the proper order, that just doesn't happen a whole lot
it could also be described as a Continuity Snarl
before it became big enough to be in danger on snarling