The bug

In Programmer Art, the angry wolf texture has the back part of its mane texture rotated upside down, unlike other wolf textures. This is caused by the changes made to models in beta 1.8, all other wolf textures' mane were swapped after this version, except for this one. The issue persisted for years but it never was reported.

To reproduce:

• Enable the "Programmer Art" resource pack.

• Summon a wolf near a sheep with infinite resistance, following the commands:

/summon minecraft:sheep ~ ~ ~

/effect give @e[type=minecraft:sheep,limit=1] minecraft:resistance infinite 255

/summon minecraft:wolf ~ ~ ~

• Try to enter inside the wolf's body in spectator mode and wait until it becomes angry.

→  The back texture of wolf's mane will rotate nonsensically.