What does Diglett scratch with?
Diglett and Dugtrio learn Scratch and Slash in gen 1. What should we suppose they are slashing with? Do the parts of them inside the hole look like little moles? Is there some depiction in the anime or otherwise of the bit of Diglett that's inside the hole?
If I was on the dev team I might have gone for Headbutt over Slash. They do appear to be mostly head, after all.
According to https://bulbapedia.bulbagarden.net/wiki/Diglett_(Pok%C3%A9mon)#Trivia :
Its ability to learn moves like Scratch and Slash imply it has claws on its hands and feet.
Also, a Diglett in Pokémon Mystery Dungeon: Red/Blue Rescue Team mentions that it has feet, though their size and appearance are unknown.