Shouldn’t use Watterson’s work. He fought long and hard against stuff like this…
Could you link to more information about this?
Here is a wiki source (insert error bars here) discussion of his stance on his work being officially licensed. He thought that use of his work outside of a comic strip would cheapen the value of the strip itself. This was frusterating as a child (who wouldn’t want a fucking Hobbes plushy) but now later I can see that it was at the very least a very defensible choice. Compare how people feel about C&H vs something that was commercialized to death like Garfield. Anyway, hope it’s useful.
Licensing

Bill Watterson is renowned for his insistence that cartoon strips should stand on their own as an art form, and he has rigorously forbade the use of Calvin and Hobbes in merchandising of any sort. This insistence stuck despite what was probably a cost of millions of dollars per year in additional income for himself and the Universal Press Syndicate. He thought it would cheapen the strip when merchandised. Watterson shared some of his issues with licensing in The Calvin and Hobbes Tenth Anniversa

The Calvin and Hobbes Wiki