Richard Feynman was giving a lecture and, as usual, had gone off-script. He mentioned some historical event, but got the last digit of the date wrong (like 1951 instead of 1957 or something). He said, "Hey! 3 significant digits is pretty good for a theoretical physicist!" :-)
Edit: I can't link to the middle of a Silverlight presentation, but if you visit http://research.microsoft.com/apps/tools/tuva/ , click the middle (with the picture of Feynman), click Lecture 5, and skip to 17:00 in, you can see the incident. But you really should watch all of them, especially the one on Symmetry.
