I know you were kidding, but one of the co-authors of Browsix wrote the Doppio JVM: http://doppiojvm.org/ a full JVM in pure JavaScript. It will soon run under Browsix!
and be sure to run a browser inside the JVM to check webmail.
Throw on Emacs and it's system-in-a-system and you'll have an infinite mirror of horribleness.