The vivid imagery of the first lines of the verses make almost anything that is not frozen or cold instantly welcome, and the image of "greasy Joan" keeling the pot (that's "cooling" the pot, to modern readers) is definitely amongst these things. The fact the her pot needs to be "keeled" in the first place also means that it was hot beforehand as well, which is precisely the opposite image of what is provided earlier in the verses of the song. Though there is not a major twist in the intellectual direction of the poem or in its form, then, there is a definite shift in the imagery of this song/poem that makes Shakespeare's meaning all the more clear. It is variation that makes life -- and literature -- exciting, and...

The twists are more clear and more deeply rooted in some poems as opposed to others, but in each of the examples here the end of the poem comments on the beginning, changing each poem's overall direction and meaning into something often completely other than what was expected. This has the interesting effect of making Shakespeare's meanings more clear, and the emotive impact of his poems even ore profound and powerful. It is Shakespeare's knowledge and utilization of dramatic structure that made his plays such fantastic and enduring stories, and this same elements can be see in the construction of his poems.