What's Mullet Fingers's name?

In the story, Mullet Fingers's real name is Napoleon Bridger Leep. We learn his real name in chapter 21.
In the chapter, Roy tells his mother about the scene Napoleon's mother, Lorna Leep, made at the student protest. Accordingly, Lorna put on a melodramatic display of emotion regarding her supposed reconciliation with Napoleon.
When Roy's mother voices hope that Napoleon's relationship with his mother will improve, Roy tells her the truth: Lorna was just putting on an act for the cameras.
In the story, Napoleon doesn't use his real name when interacting with others. His step-sister, Beatrice Leep, tells Roy that her brother always goes by the name Mullet Fingers.
When Roy asks her why, she explains that her step-brother can actually catch mullet, a slippery baitfish that swims in groups of hundreds.
Beatrice also reveals that Mullet Fingers values independence. He escaped from a "special school" in Mobile, Alabama, because he couldn't abide by the rules there. It's clear that Beatrice is extremely protective of her step-brother.
At the end of the story, Mullet Fingers disappears again, but not before leaving a baby mullet in Roy's shoe to prove that his nickname has been well-earned.