He has orange hair, sky blue eyes and appears to be a little chubby. He wears a white shirt with a green bow tie, olive pants, and brown boots. In "Money Broom Wizard" he has a yellow shirt, brown pants and brown shoes.
As far as his looks would suggest, Breehn has a high intellect amongst the few students in Ms. Baker's class. It is shown that he is way above average in his intelligence, scoring high rankings on tests and takes within great pride for this gift as shown in "Average Jeff". He also keeps himself well grounded at often times and acts much a like babysitter to Clarence and company when he is apart of their adventures. He tends to worry about things when they get bad like messes or when someone gets hurt, showing he is very cautious, as shown in "Dinner Party" where he's seen panicking after Clarence hurts himself from grabbing the insulation. He's also shown to be generally careful when doing things such as when he was performing a science experiment in "Honk". This behavior is likely the result of his family's meticulous and persnickety lifestyle and his parents' strict sense of discipline towards him. This is demonstrated when he constantly tells Clarence and the others to be careful or else his parents will ground him or when his mom is seen giving him a cold glare when Clarence asks about going to the attic which wasn't allowed.
However, for as nervous and submissive as Breehn comes off as, he has been shown to have a rebellious side to his character. In the episode "Zoo", Breehn's peanut allergy forces the class to skip a lot of the exhibits in the Zoo which frustrates them. So later when the class has lunch, to show his mettle, Breehn voluntarily accepts a peanut butter sandwich from Percy (who didn't know that peanut butter is made from actual peanuts) and when Percy tells Ms. Baker he did this, he quickly eats and swallows it despite Ms. Baker telling him to spit out and refused. It should be noted though that when his allegies kick in later and he ends up being taken away in by an ambulance, he shows clear regret, saying that "It wasn't worth it.". Also in "Puddle Eyes" Belson pretends he is away and Breehn says "What? I'm right here!"