Its head sports an altered form of whiskers made of metal. When in communication with its comrades, its whiskers wobble to and fro.
– Pokemon Sun Pokédex
Alolan Diglett doesn’t look very different from normal Diglett, it has 3 golden “whiskers” made of metal. The hairs are probably based on Pele’s hair, which is volcanic glass in thin strands.
Alolan Diglett has slightly more Defense and slightly less Speed than its normal version