How much of art history is a joke between painters. When Brueghel painted the two plump guinea pigs beneath two Rubens' lovers, was that parody? Is the motif of hands with velvet between fingers a signal between painters through the centuries? Surely most of Manet's was taking the piss. He knows that we know that he knows. He knows. And Monika Baer's somehow accesses this whole history of in-jokes with a single red clown nose.