For various reasons, I’m constantly swapping between a PC and a Mac during the day. I use a KVM much of the time, but when I need to use both machines nearly simultaneously, I often resort to Remote Desktop Connection (RDC) to control my PC from my Mac or VNC (OSXvnc and VNC Viewer) to control my Mac from my PC.
One day, without realizing it, I used my Mac to RDC into my PC which was VNC’d into my Mac, and the results were quite recursive:
Twisted. The weirdest part was the mouse handling; moving the mouse cursor over the RDC window would continually reposition the mouse cursor above the RDC window. Try it at home!