Laugh-In. Or, to give its proper name,
Rowan & Martin’s Laugh-In (1968-73), a TV series and pop-culture phenomenon whose second and third seasons ranked #1 in the ratings. This whirlwind of the sophisticated and corny was certifiably hip, hot and happening, “what it is” and “where it’s at”. Seemingly everyone in America watched it and quoted it, and everyone in celebrity-land vied to get on it. You kind of had to be there.
The gravy train ended when the public tired sufficiently to drop the show from the Top 30 during its sixth season of 1972-73, just as the Watergate scandal was ramping up and the Vietnam War was still in mid-mire. Maybe it was harder to laugh, or more likely the novelty wore off.