Reminds me of the time I was on a Lisp Machine and did

  (trace format)

This causes a line to be printed every time FORMAT is called, showing the arguments it was called with. Well, FORMAT is Lisp's printf -- it's used everywhere, including by TRACE. Oops!!! Time for Ctrl-Meta-Ctrl-Meta-Rubout! (That was the key sequence for an immediate reboot. Interesting how it prefigured the IBM PC's Ctrl-Alt-Delete.)