For diglet using scratch,slash,cut,ect,ect. I always figured that diglet/dugtrio just built up speed and "ran" past the opponent. Think sandpaper-like skin.
Forretress, Tangela/Majambo, Duskull etc, anybody?
There's all curious when you think about it, but when you aren't, they're just Pokemon...
I belive that Cubone's head looks like Charmander's head only his nose is longer. Digletts and Dugtrios don't have hands and legs. They are like earthworms...ahhh... only much much shorter.