Nerd Creeper

The nerd creeper was a hostile mob present in the April Fool's Java Edition 3D Shareware v1.34 update.

Spawn
Nerd creepers spawn when the player uses the cheat code "NEEEERD". Creepers in this version have an NBT tag called (1 = true/0 = false) that determines whether the creeper is a nerd.

Behavior
Nerd creepers, effectively being a reskinned creeper, shared almost all of their behavior, except when killed, they dropped the 3D item.