
The
show was filmed in front of a live audience, whereas most shows at
the time had a “canned” laugh track.
The
show was filmed with three cameras at once rather than one. This is
so that the director didn't have to call for multiple retakes of the
same scene (which would have been difficult for a live audience).
Even when actors bungled their lines, there usually wasn't a
retake—instead, everyone played off the mistake for extra laughs!
Desilu
(Ball's and Arnaz's production company) pretty much invented the
rerun. When Lucille Ball gave birth to Ball's and Arnaz's two
children, she needed a little time to recover before going back to
work. So episodes of the show that had already aired were aired for a
second time – and, it turns out, were very popular.
This montage of famous bits from the show starts with the really, really famous chocolate-candy-factory scene.