Forgery

A forged painting is the outcome of a fake painting bought from Redd in his shop in the city. There is no way to tell a fake painting from the real one until you either try to sell it to Tom Nook or donate it to your museum (if you talk to Redd manually after you buy a painting and he praises you, he says "Heh heh heh...." Hence his shadiness, this is not a clue towards whether it is a fake or not). Both Blathers and Tom Nook will deem it a fake and will refuse to buy/ accept it. The item then changes in name from the bought painting's name to "forged painting" (for example, if a you buy a proper painting from Redd, and it is declared fake by either Tom Nook or Blathers, its name will change from "proper painting" to "forged painting"). A forged painting is worthless, and you cannot get a refund on it. However, it may still be displayed as furniture in your house and the image will be that of the original painting's.