Wario

Wario is one of the seven star children and an adventurer and treasure hunter. He is also the founder and CEO of WarioWare Inc. Wario once hated Mario, but has since buried the hatchet with him and assumed a more friendly rivalry with him instead.

Super Mario Land 2: 6 Golden Coins
While Mario was away in Sarasaland, Wario took over his castle and made it his own.

Mario
Mario and Wario have known each other since they were babies.

Waluigi
Waluigi is Wario's partner in crime, and they often get into various mishaps while executing their plans.