* Gregory "Greg" Ridley: The main protagonist, a sixth-grader who finds himself in a sticky situation after starting a lunch-money loaning business. He's resourceful, clever, and tries to do the right thing, even when it's hard.
* Michael "Mikey" Danville: Greg's best friend, who initially helps with the loaning business but later becomes concerned about its ethical implications. He's loyal, kind, and often acts as Greg's voice of reason.
* Ms. Jewls: Greg and Mikey's teacher, who becomes suspicious of their unusual behavior and tries to uncover the truth about the loaning business. She is observant, fair, and ultimately helps Greg learn from his mistakes.
There are other supporting characters, such as:
* Richard "Ricky" Vallone: A popular and wealthy student who becomes Greg's first customer and also his most demanding one. He's often selfish and arrogant.
* Arthur "Artie" Tobinsky: A nerdy, introverted student who becomes Greg's accountant and helps him keep track of the loans. He's helpful, kind, and loyal to Greg.
These are the main characters in "Lunch Money." They each contribute to the story's central theme of the consequences of our actions, the importance of honesty, and the complexities of friendship.