Theory:

The poem "Whatif" by Shel Silverstein contains a series of questions. Here, the speaker can be seen worrying about situations that may or may not happen.
 
Most of the lines in the poem begin with "whatifs", where the speaker wonders what if something bad and bizarre happens to him or her.
 
Though the poem doesn't reveal much information about the speaker, it could be understood that the speaker of the poem is a young child, and more likely a boy. This could be guessed from the series of (childlike and boy-like) concerns that the speaker raises throughout the poem.
 
The lines "Whatif I’m dumb in school?", "Whatif I flunk that test?", "Whatif I don’t grow taller?", and "Whatif my parents get divorced?" reveal that the speaker is a child.
 
Moreover, the lines such as "Whatif green hair grows on my chest?" and "Whatif the wind tears up my kite?" suggest that the speaker is a boy.
 
The concerns are evidently of a child rather than an adult. The poem explores the insecure and inquisitive aspect of children. Though the questions are seemingly silly, they also reveal the imaginative mind of the kids.
 
Hence, from the reading of the poem, it is understandable that the speaker is an inquisitive, insecure, imaginative, and a growing child.
 
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The speaker having what-if thoughts