The two dragons are WarGreymon and BlackWarGreymon, while the two wolves are WereGarurumon and ShadowWereGarurumon. They all hail from the Digimon series. The dragons and wolves are two sets of twin brothers.

They call themselves the Yin-Yang Squad when they're together.

WarGreymon and WereGarurumon call themselves the Sun and Moon, while BlackWarGreymon and ShadowWereGarurumon call themselves the Shade and Shadow.

WarGreymon and ShadowWereGarurumon call themselves the Sunshade Duo, while BlackWarGreymon and WereGarurumon call themselves the Midnight Duo.