Restorer found a picture of a pig on a staircase
 

Barry Bowman, a Chicago restorer, who was assigned to the clearing of cloth "little Dutchman" Egbert van der Poole (1621 - 1644) discovered that the painting was heavily restructured in XVII century: over the grotesque raspyalennoy pig carcasses artist painted an ordinary ladder. On the opening wrote The Daily Telegraph.
According to the restorer, the carcass recorded, most likely, not the van der Pool, and another artist who made it to the buyer's request pictures. Probably he did not like the grotesque scenes.
Barry Bauman, in an article devoted to the restoration of paintings, said that raspyalennye carcasses have been a popular subject for painters of the XVII century, the Netherlands, and cites as examples two of Rembrandt's canvas with bull carcasses in 1638 and 1655's, as well as pictures of the brothers Isaac and Adriaen van Ostade.
Painting van der Pula "The barn is owned by Michigan, Calvin College. The collection of college work came through the gift of a former graduate - Cornelius Van Nyuisa. With the opening of the restorer was clear that the "American" paintings van der Pula has a pair, which is stored at Amsterdam's Rijksmuseum.
(Lenta.ru)

The usual thing! I know several such stories from the recent past. Record dead babies, cripples, old ladies and the like. That is something that should not be in a happy and carefree life cruelly banished from the picture. The fact that the "stupidity," wrote the artist, businesslike dealer adjusts for better understanding with the buyer. Although I know one case, because there the initiative came from the restorer: he sincerely believed that without the raven in the foreground image will benefit. The owner, when he saw was in shock!

And here is a well-known story with a portrait of Rokotov.
With the help of X-rays and special studies failed to prove that in fact the portrait depicts a woman with Tartar features and on top of it written by "unknown in the cocked hat." And in the first and the second case, the artist Rokotov wrote one and the same person - the first, who dies in childbirth, the wife of his friend, the poet Struyskogo Olympics. Apparently, Nicholas Eremeyevich ordered to alter a woman in a man, so as not to disturb the delicate feelings of a new young wife, and not to bring her jealousy.