Answer
In "Furious 7," Cody and Caleb Walker, Paul Walker's real-life brothers, stepped in to help complete the film after Paul's tragic death during production. They served as stand-ins and performed various scenes, with their faces digitally replaced by Paul's using CGI technology. This allowed the filmmakers to finish the movie while still honoring Paul's memory and preserving the integrity of his character, Brian O'Conner.