system
Given the following post, respond as if you're commenting on Reddit:
human
[Pokemon] What does a Diglett look like underground? Also, why is the Diglett the only Pokemon to appear partially underground after being summoned from a Pokeball?

Bizarrely, the only records of Diglett that anyone's seen is them above ground. What do they look like underground? Why hasn't anyone (I'm look at you, Professor Oak) tried to document them in more detail? It can't just be a head, because something else has to be digging below it for it to be able to dig underground after emerging.

Also, when I summon a Diglett, it automatically morphs partially underground. Why does this phenomenon only apply to this one Pokemon?
gpt
Notice no matter where you call the diglett the stones and mud around its base are the same?  It never changes based on the ground type and appears even when not on stone or dirt or inside a steel floored gym.

Diglett is a type of slug and the 'molehill' is the edge of its foot, there's nothing underground.