Reynie Muldoon ― Reynie Muldoon is a twelve-year-old boy who lives in an orphanage and has no friends. In the orphanage, Reynie has a special tutor since he is so much smarter than the other children. With the help of his tutor, Ms. Perumal, he enrolls in a program he saw in a newspaper ad to test his intellect. He may be surprised by the results.
George Washington (Sticky Washington) ― Sticky Washington is the second contestant to make it past the mind-bending test. Sticky has made it all of the way to the final stage, which has a twist to it. After the test is finally over, he and Reynie become very good friends and are spending a lot of time together. Sticky has many fears including darkness and very loud noises. Along the way, both Reynie and Sticky meet another candidate whose name is Kate Wetherall.
Kate Wetherall ― Kate is the third contestant to make it through the mind-bending test. She ran away from home when she was a young girl. When she was a little older, a traveling circus family took her in, and she became a part of their circus act. She learned how to walk on her hands and do other tricks which help her pass some of the tests she takes.
Constance Contraire ― Constance is a very poor girl who does not have a home to go to every night. Before she came to Mr. Benedict's house she was living in an abandoned library or the subway. Although she is a poor girl, she is very rude and does not have any manners. She talks back to Mr.Benedict even after he gave her food to eat. Even though she does not have much, she still shows no appreciation to anyone who tries to help her.
Ms. Perumal ― Ms. perumal is Reynie Muldoon's school tutor who works at the orphanage. She was picked to be Reynie's tutor because she is very smart and is able to keep up with and teach Reynie. She was the one who inspired Reynie to enroll in the mind-bending test. She is also the one who helps Reynie deal with the teasing he receives from other children at the orphanage.
Mr. Benedict ― Mr. Benedict administers the test for the gifted children. He comes up with the different elements of the test with his partners, who are named Rhonda Kazembe, Number Two, and the Pencil Woman. He is a very smart man but he has one little problem. Sometimes out of nowhere, he will just fall asleep, and Number Two and Rhonda Kazembe will have to catch him. Every year when four talented children make it to a certain level, Mr. Benedict forms a team to go on a special mission. This year, Constance, Reynie, Stcky and Kate are members of the team.
Number Two ― Number Two is the third assisstant of Mr. Benedict. He is always there for him when he falls asleep. Without him Mr. Benedict would not have succeeded with his special mission.
Rhonda Kazembe ― Rhonda works for Mr. Benedict. She is a grown-up woman who disguises herself as a young girl. She has green hair and is very short and easily passes as a young girl when she is in disguise. Every year when they administer the tests, she pretends to be one of the test-takers. She then tempts the contestants with the answers to see if they will cheat.
The Pencil Woman ― The Pencil Woman is another one of Mr. Benedict's assistants, who administers the writing portion of the test. Reynie was never told her name so Pencil Woman is how he refers to her. She directs the children from room to room and is the one who reads the rules and tells the children what and what not to do. She does not have very good manners and refuses to talk to Reynie when he needs help. The Pencil Woman is only there to correct the tests when they are done and tell the children whether or not they passed and can move on to the next round.