Symbolism, Imagery, Allegory
Who would have ever thought that a humble electric blanket would cause such a ruckus? Despite the fact that it's a ho-hum device that many people have in their homes, it is eventually revealed that the electric blanket is the catalyst for Bobby's strange transformation. He figures it out while he's sleeping one night and wakes up convinced that it's the cause:
And off and on, all night long, I keep thinking about my electric blanket. It's definitely faulty. It definitely puts out an energy field. And I definitely spent the last seven hours of my life as a normal person tucked underneath it. (19.1)
Because the blanket is what causes Bobby's change, it comes to represent unexpected change. Even though it's this object that is supposed to provide comfort and warmth, the blanket throws Bobby's life into chaos, forcing him to go outside of his comfort zone and figure out what he wants his life to look like… whether he's visible or invisible.
Importantly, though, the blanket isn't just part of the problem—it's part of the solution, too. When Alicia suggests Bobby try sleeping under to see if doing so makes him visible again, he takes her advice and does so pronto, without consulting his dad or anyone else. But while waking up invisible is a rude surprise, waking up visible is the result of a deliberate decision on Bobby's part. Because of this, as a whole the electric blanket represents Bobby's journey in the book from lost and confused to running the show.