Isaac's personality throughout his time on the series has evolved quite a bit since his introduction. At first, he was shown as a timid, shy young man whose abusive father caused him to be fearful of those around him. After Derek Hale gave him the Bite, however, Isaac took advantage of his new powers and enjoyed using them to dominate others, enjoying the feeling of being powerful instead of powerless for the first time in his life. However, after meeting Scott McCall and the members of what would eventually become the McCall Pack, Isaac eventually grew into a more selfless and compassionate person who was capable of having healthy relationships with others. Throughout all of this development, certain parts of Isaac's personality have stayed the same, such as his sarcastic sense of humor and his ability to hold grudges against those who have wronged him. As a result of the abuse he sustained from his father throughout his adolescence, Isaac developed a severe case of claustrophobia due to the many hours he was punished by being locked in a deep freezer in the basement, though he has been shown to overcome this phobia in life-or-death situations. This abuse also led him to develop a strong sense of self-preservation. Isaac also has a very blunt and honest personality that often causes him to respond to questions and statements in a harsh and/or tactless manner. He also is a somewhat pessimistic person. He also has a bit of an impulsive streak in him as well, as he has a tendency to want to fight first and ask questions later. Despite the qualities he possesses that could be considered negative, Isaac has proven himself to be an incredibly loyal person, and is willing to put himself in harm's way in order to protect his loved ones. Isaac is a very tall and very handsome young man with a lean, muscular build. He has dark blond hair that is slightly curly, pale white skin, and large, deep-set blue eyes. At first, Isaac dressed like most young men his age in simple t-shirts and jeans, but after receiving the Bite, he started to dress in a more trendy fashion, favoring designer jeans, cardigans, v-necks in shades of white, blue, and black, and black leather jackets with boots. He is also notable for enjoying to wear trendy scarves.