The Sky Is Falling (1947)

The fox convinces the duck that the sky is falling, and the duck tells the hen, and both of them tell the pig, and the three of them tell the King and, the next thing anyone knows is that the whole kingdom is twatting and twittering over the upcoming catastrophe, with the exception of the one who started the rumor. But Mighty Mouse flies in, with a song on his lips, and sets matters straight.