In Animal Crossing, Sahara is a camel who will come to your town on Saturday or Sunday at a random time of day. When she comes, you can buy carpets from her. For 3,000 Bells and a carpet you no longer want, she will give you a carpet that is not available anywhere else in the game. However, after you buy a carpet from her, the price will double the next time. For example, if you pay her 3,000 Bells for you first carpet, it will cost you 6,000 the next time.
In Wild World, however, it is different obtaining her items. She will appear sometime Monday through Friday at a random time, only to obtain her prizes, you must deliver goods to her customers in your village. She now gives you carpets as well as wallpapers for your good deeds. However, if you do not deliver her goods before she leaves, you will not earn anything.