Blimey! What's going on here?
The Moonlander, built by Yuri Landman for Lee Ranaldo of Sonic Youth, is an electric guitar with an extra set of 12 sympathetic strings. While guitars with sympathetic strings are nothing new (e.g. the Coral Sitar) this is the first guitar I've seen to employ a double-deckered headstock. (Note, by the way, in the headstock photo the alternative stringing of the six strings on the neck).
And if you think that's mad, check out some of Yuri Landman's other creations, such as the Moodswinger. Take a look at these highly intriguing pages while you can before Wikipedia goes and deletes them, although there's more to be found at www.hypercustom.com.