[19:00:34] [LayerHopper] YOU HAVE ENCOUNTERED A MOB THAT BREAKS LAYER HOPPER!
[19:00:34] [LayerHopper] MOB NAME: Orgrimmar Grunt
[19:00:34] [LayerHopper] MOB GUID: Creature-0-4469-1-8-3296-001528592B
[19:00:34] [LayerHopper] ZONE: Valley of Strength, Orgrimmar
[19:00:34] [LayerHopper] PLEASE SEND THIS INFORMATION TO KUTANO (OR REPORT ON GITHUB github.com/psynct/LayerHopper)!

I too am getting this a lot from the burning crusade version of classic from Stormwind mobs mostly.

[09:48:17] [LayerHopper] MOB NAME: Stormpike Emissary
[09:48:17] [LayerHopper] MOB GUID: Creature-0-4392-0-13314-15103-0004316ACD
[09:48:17] [LayerHopper] ZONE: Trade District, Stormwind City
[09:48:17] [LayerHopper] PLEASE SEND THIS INFORMATION TO KUTANO (OR REPORT ON GITHUB github.com/psynct/LayerHopper)!