Inevitable, but very well executed, the "hologram" of Tupac (not an actual hologram, really a kind of Pepper's Ghost), matted into the "Help me Obi-Wan Kenobi, you're my only hope" sequences from Star Wars.
R2-D2's Other Message (Thanks, Fipi Lele!)
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I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.