From Cassettes Won't Listen to Crystal Castles to Jamie Lidell, we've seen a few videos recently where folks wear prosthetic heads (see also: Robyn and the Teddybears on Letterman last night). In the video for "Gravel," it's a gal riding a bike Disney-style and singing the falsetto of Mitch Davis, aka Orba Squara, aka the guy who wrote that iPhone ...