It was given to him by his mother when he turned 5. Ever since then, he has completed every assignment with it, even Math!
One day in 7th grade, he dropped it underneath his desk and he couldn't find it. This made Brian very sad, as he had to go home and write his homework with a crummy pencil. The next day, he walked into class, only for his teacher to hand him his beloved writing utensil. From that day on, Bran swore he would never lose his pen again!
It has a starring role in The Breakfast Club as the pen he uses to write the essay summarizing everyone in Detention.
Little known fact, Brian's pen was actually John Hughes personal pen that he spent half of the movies' budget on.