Litigation
The script development was the subject of a famous copyright lawsuit, Anderson v. Stallone, 11 USPQ2D 1161 (C.D. Cal. 1989). Anderson developed a treatment for Rocky IV on spec; after the studio decided not to buy his treatment, he sued when the resulting movie script was similar to his treatment. The court held that Anderson had prepared an unauthorized derivative work of the characters Stallone had developed in Rocky I through III, and thus he couldn't enforce his unauthorized story extension against the owner of the character's copyrights.
Read more about this topic: Rocky IV