Physically, Phillip Malloy is described as being "a nice-looking boy" by Margaret Narwin. Aside from that, little detail is given about his physical appearance. It is known that he is a star runner, so it would probably be fair to conclude that he has a classic runner's build, thin perhaps, and wiry, but strong.
Emotionally, Phillip is a very complex character. He is an only child, and used to getting his way; Margaret Narwin notes this, and the fact is further evidenced in the way Phillip's parents are so quick to offer to intervene for him in his dealings with Ms. Narwin, whom he says "has it in for (him)." As an only child, however, Phillip is under a lot of stress as well. Although they seem to coddle him, his parents, and his father in particular, have specific expectations for him, most having to do with following in his father's footsteps. In school, Phillip is used to taking the easy way out. He makes no effort at all to learn the material when Ms. Narwin assigns the class to read The Call of the Wild, planning from the very beginning to "figure a way to run past Narwin." Phillip is quick to want to manipulate the system for his own benefit; he only starts to worry about his grade in English when he realizes that if he does not do well, he will not get to run on the team.
There is evidence that Phillip is not a completely depraved character, however. He declares he likes math, even though he knows that the other students will ridicule him if they ever heard about his interest in the subject. His tendency towards working hard at endeavors that interest him, such as math and running, show that he has potential, but sadly, his stubborn inclination to always take the easy way out of situations which do not appeal to him stunts his emotional growth and leads to his downfall.