Just like the title says, make a movie by mashing up two movies that share an actor, except now they’re both characters at once.
So taking Mr. Smith Goes to Washington and The Man Who Shot Liberty Valence with the commonality of Jimmy Stewart gets us a movie where a lawyer in the Old West gathers up his courage and kills a hated gunman and the then uses this to springboard into being asked to fill a vacant Senate seat.
Or, taking Darkman and The Grey with Liam Neeson, we get a movie about a scientist who loses his face in a lab accident then takes vengeance on the mobsters who caused it. After fixing his face, he realizes that vengeance wasn’t really worth it and he moves to Alaska as an sharpshooter for an oil company to mourn his lost life. There he discovers the value of life after he’s in a plane accident and forced to survive in a harsh wilderness.