Very interesting. It's not animated on the LC III/Performa 450 either as far as I can tell. But the LC III ROM also contains normal 32x32 images of the complete happy mac and sad mac. The Classic does not. It must use one of these three animation frames, with mask, and place the appropriate 16x10 image on top of it.
Based on what you said, Tempest, I can only assume that this image is assembled behind the scenes and makes it to the screen in one piece.
Browsing my ROM collection, as incomplete and possibly having bad dumps as it is, I can date these "animation" frames back to the IIfx, but after the IIci. Checking several other Macs before the IIci also turned up nothing.
Based on what you said, Tempest, I can only assume that this image is assembled behind the scenes and makes it to the screen in one piece.
Browsing my ROM collection, as incomplete and possibly having bad dumps as it is, I can date these "animation" frames back to the IIfx, but after the IIci. Checking several other Macs before the IIci also turned up nothing.