Pokemon Go Sinnoh Celebration event: Shiny Riolu and Hippopotas released - Dexerto

The Pokemon Go Sinnoh Celebration event brings back an array of Gen 4 Pokemon including shiny Riolu and Hippopotas.

Shiny Pokemon GO Sinnoh And Valentine's: Chansey, Riolu, Happiny, Hippopotas! - SlashGear

Sinnoh Celebration event research tasks explained in Pokémon Go

Sinnoh Region Celebration - Leek Duck

Sinnoh Region Celebration - Leek Duck

Event Gameplay Pokémon GO Tour: Sinnoh – Los Angeles

Sinnoh Region Celebration - Leek Duck

The Shiny Pokémon That Will Release During Pokémon GO Tour: Johto

Sinnoh Celebration Event

Sinnoh Celebration - Pokémon GO

Pokémon Go' Sinnoh Event: Start Time, Shiny Riolu & Everything You Need to Know

Sinnoh Celebration, Pokémon GO Wiki

Sinnoh Region Celebration - Leek Duck