Download the Forecast Channel for the Wii and keep you system online. If connected, the weather during the game will be the same as the weather in your city (e.g. If it's raining in your town or city, it will be raining in the game).
Complete the Gerudo Training Ground
Beat the race at Lon Lon ranch for Epona, and then race again and get a best time (49 seconds or below). This unlocks a cow for your tree house.
Enter this code at the main menu screen: (Hold 1) Up Up Down Down Left Right Left Right (Release 1)