The 49-year-old "Hannibal" star, who recently gave an autograph on a fan's Star Wars poster also wrote the word "Galen" (Galen Marek, codenamed Starkille) underneath, reported Digital Spy.
The poster was also signed by Phil LaMarr, who wrote his "Star Wars: The Clone Wars" character name Kit Fisto.
The spin-off movie, also starring Felicity Jones and Ben Mendelsohn, will be based around a group of rebels looking to steal blueprints to the Death Star.