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There are 6 different kinds of fruit in the world of Animal Crossing. Your town will start out with a random fruit. The fruit you can get are: an apple, a pear, an orange, a peach and a cherry.

When you try to sell your designated town fruit to Tom Nook, he will give you 100 bells for each piece. If you get fruit from an other town he'll buy it for 500bells.

[edit] The coconut

When you go to the animal island, you can get coconuts off the trees. You can only plant them near the beach. Tom Nook will buy them for 500 bells a pop.