It's interesting to compare this with French-language comics where often the rights to the series are tied to a publisher who will have different authors work on it over the years, but the rights for secondary characters created by that author remain with the author, which if no agreement is reached can result in an entire roster of secondary characters dropping out of existence with no explanation between two stories as the previous author leaves and takes their characters with them.
Thus the series Spirou and Fantasio's most iconic run was that of Franquin (from 1948 to 1968) (the character of Spirou was first created in 1938), who created most of the series's iconic secondary characters, including the marsupilami, their weird monkey-marsupial-like animal companion.
Then when Franquin was succeeded by Fournier, none of the secondary characters created by the former could be used, so they just stopped appearing. There was no explanation or even mention of them, the comic was now effectively taking place in a different reality with an entirely new cast of secondary characters that everyone acted as if they were already established.
Then after Fournier left in 1980, this happened again with his characters, and so the new authors Nic & Cauvin had to create again a set of secondary characters from scratch and act as if they had been there all along with no acknowledgement of previous characters.
However, when Nic & Cauvin left in 1984 and Tome & Janry took over, Dupuis managed to negotiate with Franquin (who was still alive and doing his own stuff) for the right to re-use most of his secondary characters, so at that point the comic reverted, again with no explanation, to the "classic" cast — except for the marsupilami who Franquin wanted to keep the rights of because he had his own standalone series, and would not appear in another Spirou story again except for a one-off in 2016.
