Mac Themes Garden features a collection of nearly 4,000 Classic Mac OS GUI customizations you don't want to miss out on.

The Appearance Manager even had a "scheme to theme" feature, which translated Kaleidoscope schemes into Mac "themes." Aqua, the much-lauded look and feel of OS X, is essentially an updated OS 9 theme.

Just as it's not possible to see what Android 1.0 was like when it was new, installing Mac OS 9 on an old PowerBook in 2014 does not actually show you what it was like to use Mac OS 9 in 1999.