I've encounter an occasion where an NPC is walking around on the map and it's polygons go out of wack.
Basically you see "stringy" animations expanding and rotating. It almost looks like it's part of the NPC, but clearly it isn't.
Dell XPS 630i
Win7 64-bit
Intel Core 2 Quad (Q6600) 2.4 GHZ
4GB Ram
ATI Radeon HD 5870 (1gb)