At first he discovered [J] that the iBook screen space fits iPad well. Then he managed to put Apple Keyboard. Lastly, to connect iPad and keyboard by iPad Camera Connection Kit within the small space around the iPad, found the good extension cable [J].
Now iPad users can enjoy Macintosh experience.
via @otsune [J]
[Update 2010-06-11] Another Japanese blogger hirac made an iPad Stand By Macintosh Classic [J]