Why is Jeffrey memorable and unusual in Maniac Magee?

Pretty much everything about Jeffrey Lionel Magee is memorable and unusual.  First of all, there is the way he frees himself from ridiculous and uncomfortable living arrangements with his disfunctional Aunt and Uncle.  During a spring musicale at his school, Jeffrey just starts screaming during a song he and his class are performing onstage.  When the song is over, he continues to scream, then leaps off the stage and runs out the auditorium door, "Never again to return to the house...Never again to return to school" (Chapter 1).

After the scene during the school performance, Jeffrey disappears for a year, then reappears two undred miles away in the city of Two Mills.  No one knows what happened during that "Lost Year", but people do remember what the "scraggly little kid" does when he jogs into Two Mills - as he passes by the people, he says "Hi".  That is unusual, because "people just didn't say that to strangers, out of the blue" (Chapter 2).

Jeffrey has amazing athletic abilities.  He stops by the high school on his first day in town, and as he runs across the football field, intercepts a pass and carries it, "weaving upfield through the varsity football players".  No one can catch him, and when he gets to the end of the field, he makes a perfect punt back to the hands of the receiver who was supposed to catch the pass in the first place.  Jeffrey then runs off, leaving the players stunned (Chapter 4).

A little later that same day, Jeffrey makes an appearance at the Little League field in the park.  He nonchalantly steps up to the plate to face the legendary John McNab, who has a vicious fastball and has just struck out sixteen batters.  Even though Jeffrey is much, much smaller that McNab, he manages to his four home runs off the ace.  Angry, McNab lobs a frog up to the plate instead of the ball, and Jeffrey gently bunts it, running all the way around the bases while the fielders try vainly to retrieve the happily hopping frog (Chapter 7).

In addition to showing amazing prowess in sports, Jeffrey is also fearless.  All the neighborhood kids are terrified of Old Man Finsterwald and stay far away from his house and yard, but Jeffrey casually makes himself at home on the Finsterwald porch, stretching out and reading a book there (Chapter 5).