WaWaWaluigi can be seen at North Hyrule where he lives in a hotel room, where he smokes at. His apartment is actually underneath the hotel where Wa clones live. If you want to go there, ask an employee nicely for the key to the bottom of the hotel. But be careful because WaWaWaWaTinky-Winky, Shadow Bonnie & Shadow Freddy and the WaTubby Toast Legion roam there, and they would definitely kill you. WaWaWaluigi also has rabies so he could kill you too.