"You would have to be half mad to dream me up," is a quote from Lewis Carroll, famously capturing the whimsical and imaginative nature of his work. It suggests that the ideas or characters he creates are so fantastical that only someone with an unusual mind could conceive them.

In the context of E.K. Blair's book Echo, this quote emphasizes the idea of extraordinary or unconventional characters and stories. It highlights how some narratives and personalities might seem surreal or outlandish, yet they add depth and intrigue to the literary world, challenging readers to see beyond normal perceptions.