I was experimenting with Leopard Screen Sharing and its backwards compatibility with VNC - see "Screen Sharing with Leopard Extends to Tiger," 2007-10-26 - when I managed to produce this lovely recursive screen capture.
I was using Timbuktu Pro 8.7, the new Leopard-compatible release, to connect to a test system I have that's running Leopard. With Remote Desktop enabled on my main Tiger computer, I connected back from Leopard. Leopard and Timbuktu Pro gamely redrew each recursive window in alternation. What a partnership. The two programs kept drawing smaller and smaller screens - look in the middle left to see teeny tiny forms of the whole.