Answer:
Character changes and a striking resemblance between Laurie and Charles suggest that Charles is actually Laurie in the story "Charles," where the female protagonist, Laurie, is mistaken for the male protagonist, Charles.
The most obvious clue is how quickly Laurie changes from his mother's "sweet-voiced nursery-school tot" to a "long-trousered, swaggering character who forgot to stop at the corner and wave goodbye to me." This may be the clearest sign that Laurie is really Charles. Foreshadowing the inevitable conclusion that both these guys are a single person; the author provides various hints and indicators.
Step-by-step explanation:
This is my interpretation; you are free to alter it to your own satisfaction.