Elephas has the highest base Special Defense stat of all non-legendary Normal-type Pokémon.
At one point during development Elephas was supposed to have a cross-generational evolution named Mammudha.
This Pokemon is the butt of jokes most of the time, being referred to an Indian Elephant. For example, Frutagon's description states that it cut 665 Elephases in one slash, and Farfigtron's description states that its fire can melt Elephases.
Mud Shot and Muddy Water could be in Elephas' moveset as a reference to the insanely unsanitary and unsafe condition of the Ganges River in India.
Elephas is literally an Indian elephant, and its design references several stereotypes pertaining to Indian people. It is designed as a joke and reference towards the perplexing fact that Raichu and Gastly's Pokédex entries mention said animal.
Its Dex Entry lampshades this by mentioning how it can withstand electricity and is afraid of ghosts.
Despite this, Electric attacks affect it normally and it's immune to Ghost-type attacks.
Literally elephas, the scientific classification of an Asian elephant.