Arnold is the only child of an anthropologist man named Miles and a physician/botanist named Stella, both from America, and was born during their research in South America. The last time Arnold was seen with his parents was when they left him in the care of Miles’ parents, Philip and Gertrude. Arnold has been with his grandparents since and has a strong bond with them, and knows first-hand, there’s never a dull moment with them. Arnold lives in a boarding home that Philip own and helps his grandparents a lot. Arnold has a unique musical trait, especially in jazz, and rarely shows any signs of weakness in spite the odds.
Despite skilled in Martial Arts and other sports, Arnold often gets the most difficult tasks done with little to no need to fight.
- After being scolded for passing a basket ball to Gerald, instead of Tucker since it would’ve cost his school, P.S. 118, the game, Arnold has to teach Tucker on the game and his dad, Coach Jack Wittenberg, on sportsmanship which he lacked in.
- When a fellow student, Thaddeus "Curly" Gammelthorpe, took the school hostage in Curly Snaps was able to convince Principal Wartz to let him talk to Curly. The move saved the school.
- Arnold also senses if someone is wrongfully accuse of a crime, he would refuse all form of pressure, forcing everyone to rethink their moves which gets them to realize the mistake Arnold noticed.
- This was seen in False Alarm when he was able to save Eugene Horowitz despite of his bad luck.
- Sometimes, when Arnold blamed for a minor offense and refuses to tattle, the troublemakers would crack and confess to save him.
- Because of his ability to remain strong even in the harshest of pressure, other students often ask Arnold for any advice.
- During with the schools was one thing, but sometimes, an entire neighborhood seeks for his help.
- This was especially seen in the film version of the TV series when he helped save his neighborhood from a spiteful business owner who wanted to build a mall after destroying his neighborhood.
- Whenever there an urban legend, Arnold would be among the few willing to put it to rest, even if it means it could be fatal.