Cold open

A cold open (also called a teaser) in a television program or movie is the technique of jumping directly into a story at the beginning or opening of the show before the title sequence or opening credits are shown. On television, this is often done on the theory that involving the audience in the plot as soon as possible will reduce the likelihood of their switching away from a show during the opening commercial. A cold open may also be used to recap events in previous episodes or storylines that will be revisited during the current episode.

The cold open technique is sometimes used in movies. There, "cold opening" still refers to the opening moments or scenes, but not necessarily to the full duration before the title card, as the title card might appear well after the cold open has been achieved.

In the early 1960s, few American series used cold opens, and half-hour situation comedies almost never made use of them prior to 1965. Many American series that ran from the early 1960s through the middle years of the decade (even sitcoms) adopted cold opens in later seasons; for example, Gilligan's Island did not use cold opens during its first two seasons, but did use them in its third and final year (1966–67). They were used on some seasons of Mission: Impossible, likewise with Hawaii Five-O. Many other long-running TV series used cold opens; similar patterns can be seen with sitcoms, including Bewitched and The Beverly Hillbillies.

Cold opens became widespread on television by the mid-1960s. Their use was an economical way of setting up a plot without having to introduce the regular characters, or even the series synopsis, which would typically be outlined in the title sequence itself. The Man from U.N.C.L.E. (1964–68) and Star Trek (1966–69) are examples in the United States. In the United Kingdom, the format was usually utilized only in series destined for the American market, such as The Avengers (1961–69) and The Saint (1962–69).

...
Wikipedia