While Lucasfilm President Kathleen Kennedy had pledged Jar Jar Binks wouldn't appear in "Star Wars: The Force Awakens," another character from the prequels could have made a cameo.
In "The Art of Star Wars: The Force Awakens" coffee table book, concept artist Iain McCaig reveals he'd proposed the return of Hayden Christensen's Anakin Skywalker as a Force ghost, albeit unlike one fans had seen before.
“When you light a candle, you also cast a shadow,'" McCaig explains (via The Independent). "That inspired me to propose, for the first time, that Anakin’s ghost could come back […] If we see Anakin Skywalker, because he does flow back and forth between Darth Vader and Anakin, let’s see him as a character with a dark and light side. The reason Luke is this whole new entity is because he was the first to acknowledge his own dark side — that it was not separate from him.”
You can see scans of McCaig's Force ghost concept art at the fan site Making Star Wars, which notes speculation that Christensen has been cast in "Episode VIII."