ABC had to pre-empt Happy Days on October 12, 1976.

From the video description:

In 1976, ABC was set to televise game three of the ALCS between the New York Yankees and the Kansas City Royals. However, they put in a request to Major League Baseball to not do that, and instead, try to delay the start time of the game so they could show an all-new episode of Happy Days. And MLB's reaction went about as well as you'd expect to this bizarre request.

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NBC WAS successful in pushing a game of the 1988 World Series back 30 minutes, to air The Cosby Show.

I cannot name the episode, but it’s where the daughters called each other “darling.” I think in that episode they called themselves The Darling Sisters.

EDIT: Based on what I just read about the ‘88 Series, the ep was called “Rudy’s All-Nighter.”

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