"Do you think that William likes Lady Jaye?" Poppy asked […]. "Like like likes?" (1.57)
Though Zach doesn't realize it, Poppy is using the game to ask him a serious question about real life: Is he romantically interested in Alice?
It was a handshake taught to everyone on the basketball team, and every time that Zach did it, he felt the warm buzz of belonging. (2.9)
Part of figuring out who you are is discovering who you like to spend time with. Zach has two separate sets of friends—the basketball team, and Alice and Poppy—and there are things about each set that he really likes.
That past summer, the mysterious thing that had stretched other boys like taffy had started to happen to Zach. (2.23)
Detective Shmoop has cracked the case: The mysterious thing is puberty. Take that, Veronica Mars.
"He's twelve years old, playing with a bunch of crap," he said […]. "He's got to grow up. It was time he got rid of them." (2.54)
Zach's dad is in a real rush for his son to grow up, but Zach needs to come to terms with adolescence on his own time.
"We're too old anyway, don't you think?" he made himself say.
Alice looked stricken.
"That's stupid," Poppy said. "We weren't too old the day before yesterday." (4.10-4.12)
Zach tries out his dad's philosophy, but he can't make himself believe it. For the record, Poppy's not buying it, either. You go, girl.
He was the captain of a real ship, a real ship really called the Pearl. It was almost too much magic to bear, but for once he didn't question it. (11.22)
For months—maybe years—Zach's favorite toy has been a pirate that captains a ship called Neptune's Pearl. Then in real life he steals a real boat that's called the Pearl. Quite a coincidence, don't you think?
He looked back into the mirror, seeing a slightly sunburnt boy looking back at him, older than he remembered himself […]. (13.20)
Presumably, it's only been a day or so since Zach last saw himself in a mirror. Perhaps he thinks he looks older because the quest has matured him in some way? What do you think?
"Well, come on then, William." Alice's voice, from the dark, was eerily changed. It was like he was talking to Alice and the character she played at the same time. (13.78)
This is another point in the story in which a character "becomes" her toy. Alice becomes Lady Jaye, just as Zach becomes William the Blade when he steals the boat.
"I can see you changing […]. It's like you're both forgetting everything. You're forgetting who you are." (14.39)
Poppy sees growing up as a loss. But is it possible that you gain something, too? To dig deeper into this, swing by Death elsewhere in this section.
The words came easily, the way they did when he was playing, but he felt entirely like himself. (16.103)
At the end of the book, Zach demonstrates that he's no longer just a kid playing games during the Queen's funeral. He no longer needs toys because he's finally found himself.