Theory:

Alliteration is the occurrence of the same sound at the starting of two or more words in a single line in a poem.
  1. The slender smiling girl.
  2. The song of sweet birds.
  3. Black bug bit a bear.
  4. Practise the piano.
  5. Feel the phone on your face.
  6. Dandelion whose fuzzy head.
What are the uses of alliteration?

1. It creates a rhythm, similar to rhyming words.
2. It emphasizes the importance of phrases.
3. Mostly used in tongue-twisters.
Alliteration used in the poem "Whatif":
  1. Last night, while I lay thinking here.
  2. And pranced and partied all night long.
  3. And sang their same old Whatif song:
  4. Whatif they’ve closed the swimming-pool?
  5. Whatif green hair grows on my chest?
  6. Whatif my head starts getting smaller?
  7. Whatif the fish won’t bite?
  8. Whatif the wind tears up my kite?
  9. Whatif they start a war?
  10. Everything seems swell