Great question — answering as the UphillTech team:
The first (1988) draft of Back to the Future III supposedly has this scene, which was later cut in future revisions : Ironically, right then, Dean Wooster stops by with two other men named Cooper and Mintz. They tell Doc that, because he is working for them at the University (as a professor of physics!), he has to participate in one of three projects--working on the Edsel car, working on a chemical warfare thing ("They'll name the final chemical agent after you," notes Cooper. "'Agent Brown.'"), and working on something called Xerox, which Doc pronounces "X-rox." Doc, however, has no interest in any of these projects (even though Marty tries to steer him towards the Xerox one!) and refuses...
Full answer by cde: https://movies.stackexchange.com/a/41206 (CC BY-SA 3.0).
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