With his uncharacteristically lighthearted Sonnet 143, William Shakespeare plants a picture in our minds of the poet as a crying toddler placed on the ground while his mother is running after a wayward chicken, and expresses his hope, not unreasonable in the imagined circumstances, that the mother, once she has caught the bird she's chasing, will come back to him and comfort him with her affection and her love.
It's an unusual simile to say the least: not because it is complex or difficult to visualise – in fact the opposite – but because it departs from virtually all and any traditional or even just, one might argue, advisable comparison for a lover to invoke: rare is the Lothario who impresses his mistress by likening himself to her babe. And it continues to expressly accept the fact that this woman has other men whom she actively pursues. In this case, it would appear, one particular other man, who in this oddly farcical setup is assigned the role of the runaway cockerel.