Though Miranda and Sal have known each other since they were little, they are no longer friends, or so we learn. Why? We're not exactly sure yet. Think of it as yet another mystery.
The loss of their friendship hurts in many ways for Miranda. One of which is that she has to walk home alone, past the Laughing Man.
Who is the Laughing Man? According to Miranda, he's a "crazy guy" who showed up on their street at the beginning of the school year (5.2). He yells things like "What's the burn scale?" and shakes his fist at the sky (5.2). He also sleeps with his head under Miranda's mailbox.
Some people call him Quackers, but Miranda's mom prefers the somewhat less cruel name "laughing man" (5.7).
Back to Sal: Miranda really felt that Sal was part of her and that she was part of him.
When the two were little and in day care, they each had a carpet square to nap on. Sal would push his foot against hers. When Sal missed a day, the teacher put his square down for Miranda anyhow. She couldn't sleep, though, without Sal's foot there.
Now, back to the Laughing Man. He says things in a chant-like way: "bookbag, pocketshoe" (5.15).
Miranda asks Richard what a pocket shoe is. He gives her a long-winded and silly answer, and Mom calls him "Mr. Perfect" as she often does. He taps his right knee.