Mechanical Skull from a Pixie?

[Seiun_Divinity_D2]

I was playing terraria and I generically defeated a Pixie, and then a mechanical skull dropped. What are the odds of this happening?

[Tymon]

ANY enemy in the game can drop a boss summoning item once hard mode hits if that boss has not been defeated yet. Not quite sure the drop rates though. But yes, you can get mechanical eye, worm, and skull off enemies.

[Mau]

It's a 1/2500 chance from any mob in hardmode if the player hasn't beaten skeletron prime yet (Excluding meteor heads and statue spawned mobs)