Good news, everyone (I miss Futurama).
Three years ago I wrote a mootools plugin for password strength checking, based upon a stack overflow jquery post. I just had cause to revisit this for work at QMetric and refactored it (read, rewrote from scratch) for MooTools 1.4+
The Class is on the forge, it’s fairly flexible and can either be styled to use the default strength indicator or to output whatever you like based upon pass/fail events and scores.
Links to demos are in the README.md as well as a basic buster.js test suite. Use responsibly!