Joe is a young boy who serves as the leader of his friend group. For his birthday, he receives an unusual gift called "The Book," which transports him and his friends back to the medieval era of King Arthur. He possesses a talent for stage magic, a skill he learned from his uncle. When thrust into the past, he relies on his confidence and understanding of human nature to survive the dangerous setting and rally his friends.

Identifiable by his glasses, Sam is the intellectual backbone of the trio. While his friends rush into action or rely on bluffing, Sam assesses situations logically and prefers mind games over muscle. He uses his sharp intellect and cunning to outwit physically imposing threats that the traditional medieval knights cannot handle.

Fred is the athletic, impulsive joker of the trio. He relies on physical action and instinct rather than deep planning, frequently acting as the group's comic relief. He completely fails to understand the formal, archaic speech of the medieval knights and constantly requires his friends to translate for him.

Merlin is King Arthur’s court enchanter, recognized by his flashing green eyes and long beard. As the only magic user in Camelot, he commands deep respect from the king and his subjects, enjoying a unique status of influence. He views the boys as a direct threat to his position and remains highly suspicious of their modern tricks.

King Arthur is the legendary ruler of Camelot who commands the Knights of the Round Table. Despite his royal authority and celebrated warriors, he struggles to protect his kingdom from current monstrous threats and relies heavily on Merlin's counsel. He eagerly seeks help from the boys when his own knights fail.

Uncle Joe is a traveling magician and Joe's namesake. He sends his nephew a mysterious, dark blue volume called "The Book" covered in silver stars, along with a written warning to be careful what he wishes for. His career in stage magic serves as an active inspiration for his nephew.

Bleob is a gigantic, foul-smelling monster who wears red suspenders. He relies entirely on his brute strength and has successfully terrorized King Arthur's knights, who cannot withstand his physical power or his odor. While physically devastating, he struggles with intellectual challenges.

Smog is a dangerous dragon threatening King Arthur's kingdom. He serves as a massive physical danger to the people of Camelot until he is inadvertently drawn into a brutal territorial brawl with another monster.

Sir Lancelot is famed as the greatest and most skilled knight of the Round Table. Despite his legendary combat abilities, he finds himself totally outmatched by the magical creatures currently attacking the kingdom and humbly asks the modern boys for their assistance.

Sir Percival is one of King Arthur's esteemed Knights of the Round Table. Along with his fellow warriors, he is amazed by the boys' unconventional combat methods and escorts them directly to the castle.

Sir Gawain is a prominent member of the Knights of the Round Table. He represents the traditional medieval martial strength that currently proves completely ineffective against the magical monsters attacking Camelot.

Queen Guenevere is the royalty of Camelot alongside King Arthur. She acts as a willing participant when Joe needs someone to pick a card to demonstrate his stage magic to the skeptical medieval court.

The Black Knight is a heavily armored warrior who immediately attacks the boys upon their arrival in the past. He speaks in a formal, archaic manner that confuses the modern children and insists on engaging them in deadly combat.

Joe's mom is a modern-day parent who views Uncle Joe's unusual presents with severe irritation. She remains completely unaware of the true, magical nature of the book her son receives for his party, mistaking the magical effects for cheap party tricks.