If you weren't super familiar with Star Wars and lacked an encyclopedic knowledge of all the character and actors, you might think this is just an interesting picture. All Star Wars relation aside, this is an interesting picture. You've got a little person and a normal-size person riding a motorcycle together. That's going to turn some heads. A keen Star Wars viewer, however, would notice that that is R2-D2 and C3PO riding together.
If they made an opposite version of Star Wars where all the humans were droids and all the droids were human, this is how C3PO and R2-D2 would look. They'd still need some kind of rolling contraption to feel like them, so a miniature motorcycle is perfect. I'd love to see a movie like that, but can you imagine how much it would cost? That's way too many droids to build.