I Is for Imagination
Imagination is at the core of any work of fiction. The characters, the dialogue, the plot, and in some cases even the setting are imagined by the author. Certain authors are more known for their imaginations than others: Lewis Carroll, Kurt Vonnegut, Stephen King, J.R.R. Tolkien, etc. But it requires a powerful imagination to create an intricate plot, even if it's set in the real world with nothing zany happening.
I is also for illustrators: