What is the source of the allusion in the sentence below?
The weather forecast called for clear skies, making my grandfather look like Chicken Little.

 - a song
 - a fable
The source of the allusion Chicken Little is a fable.
In a well-known folktale, Chicken Little is accidentally hit by something and jumps to the conclusion that the sky is falling and that she must spread the news of imminent disaster.
The allusion Chicken Little means a person who spreads alarming news of imminent disaster.