Via Polygon.com:

The first trailer for the upcoming Star Wars: The Force Awakens has been picked apart almost literally frame-by-frame, but there are still a few surprises for fans. Mark Hamill, who is reprising the role of Luke Skywalker in the upcoming film, has revealed the rolling ball droid named BB-8 wasn’t CGI, but a practical effect.

“They never cease to amaze me with what they’re able to come up with, you know? I said, ‘How are you ever gonna top R2-D2, the most adorable droid in movie history?’ And then they have this new one. I can’t even tell you his name, but you saw it in the trailer,” Hamill told Yahoo Movies.

“And when they were demonstrating how they did this thing, live on set — because it’s not CGI, that’s a live prop — I was just amazed. They let me play around with it. [Laughs] I was running it all around at the creature shop up in Pinewood. I’m telling you, it’s an absolute delight. And not having thought that I’d ever go back there, to go back into that world, is just – I get the chills. It’s just so much fun.”

We knew the films would be putting an emphasis on practical effects over CGI, but there’s still something cool about the fact someone had to invent that crazy rolling thing and get it to work on film, and it’s stable enough that one of the actors could also control it just for the fun of it.