Answer
Peter Cushing's character, Grand Moff Tarkin, was killed in Star Wars (1977), but he appeared as a ghost in Return of the Jedi (1983). This was made possible through the use of unused footage from Star Wars that was digitally remastered and re-edited. The appearance of Tarkin as a ghost was a controversial decision among fans, with some arguing that it was disrespectful to Cushing's memory.