Did you play with Lego as a kid? I did, obsessively, but I never built a Mac out of Lego. Daniele Procida, from the uk.comp.sys.mac newsgroup, built one, and he’s selling it on Ebay.
(As the Ebay link will have expired by the time you read this, I’ve saved one of the pictures here).
And yes, it’s a fully functional Mac!