When Star Wars: The Force Awakens debuted, it rolled out a droid that was basically a soccer ball with a droid head on top. It’s obviously CGI because how was that possible? Well, we still don’t know, but at Star Wars Celebration, they brought him on stage… and he’s a practical effect.
Seriously, look at this!
Here’s a rear view. They literally brought BB-8 out on the stage and had him roll around. Look at the head in particular:
All we can say is: Holy crap.