Museum

The Museum is a white-brick building found in both Animal Crossing games. It is an establishment for the collection and display of insects, fish, paintings, and fossils. The curator, an owl named Blathers, will have to be woken up during the day.

Insects
With the net you can catch bugs in the wild, when you catch a bug that hasn't been added to the museum yet, you can donate it. Insects are kept in a grassy room with everything they need to live.

Fish
By fishing with the fishing rod you can catch fish. Fish that haven't already been donated can be given to the museum. They will be kept in tank of water the you can see whenever you wish.

Paintings
You can buy paintings from Tom Nook and Crazy Redd, or find them if you're lucky. Be warned, paintings you buy from Redd in Animal Crossing: Wild World have a chance of being fakes, and will be regected.

Fossils
Fossils can be dug up from the ground at star-shaped spots. In Animal Crossing, you will have to send them by letter to the Faraway Museum for analasis, they will be returned shortly. In Wild World, Blathers has the licence to analyze fossils himself, making the process much shorter.