I have a .doc file that had the normal Word icon. I was editing a pic in Photoshop and saved it as a JPEG. It showed up on the desktop where the .doc file was, displacing the .doc file downward on the desktop.
The weird part is that the .doc file acquired the JPEG's icon. GET-INFO of the .doc file shows the JPEG's icon, although if it's in the foreground in front of the JPEG's GET-INFO, the .doc file's icon is an Illustrator icon. (I haven't loaded Illustrator in weeks.)
The icon is for this pic:
TiBook 1 GHz, with Panther X.3.1.