Remember it’s theirs. They were there before you arrived and will doubtless be there long after you’re gone. They own that property, are likely enough to have worked hard on it in their time, and—whether they originated it or are just its buyers—are almost certainly powerfully protective of it. You can press against the edges of their envelope—quite hard, if you’re careful and have permission—but break through the fabric of their corporate reality without warning and you are going to be in deep trouble.
Do your homework. Know your licensor: know their history with other creators. Find out where there have been problems in the past and keep your eyes open for warning signs that you may be about to discover some new one. If you were lucky enough to be invited in, act like a considerate houseguest (creatively speaking). While working in that universe, don’t (for example) sneakily attempt to jettison parts of the property that annoy you, or covertly subvert bits that seem to call for subversion. (Overt subversion is a different story. Be in communication with your IP owner about this, and you may be able to win them over. [Though you should be prepared for them to take credit for this after the fact.] But I have seen people disinvited from franchises with extreme prejudice after they were caught trying to pull one or another kind of “fast one” on their publisher.) If there’s a work-with-us guide or in-house bible, sleep with it under your pillow.
