Grady his best friend Nico Harris share almost everything, even the same birthday. The two are often up to no good, usually trying to impress girls, get revenge on Chad, or bend the rules in some other way. In sketches, Grady often plays the thing that comes out of Nico (in the first episode, Nico is a chicken and Grady is an egg, Nico plays the stomach and Grady plays the barf). Nico and Grady also enjoy watching the game show Meal or No Meal. In "Fast Friends", Grady and Nico sold Tawni's stuff on the Internet for extra money, but were caught and punished by Tawni by having to be her slaves.
Grady, during a dream sequence in "High School Miserable," believed he was in love with Martha. In the episode "New Girl," Grady develops a crush on Mel Winters, a waitress at The Patio. He becomes nervous when he realizes that she might potentially be crushing on him as well and his nervous tick, which is involves Grady taking on a Scottish alter-ego named "Shamus McGregor."
Grady doesn't talk back much to anybody. When Tawni said "Now FLOSS!", Nico didn't want to so Grady flossed Tawni, and in "Randoms Acts of Disrespect", when Buddy asked Nico and Grady to help him get out of his trunks, of course none of them wanted to help Buddy so Nico walked out saying "You're my Grady!" making Grady do it.
It is possible that Grady may have a crush on Sonny. In "Promises, Prom-misses", Grady and Nico were both amazed at Sonny's look. In "Grady with a Chance of Sonny", when Sonny said that she was officially Grady's girlfriend, Grady was very happy and in the end when Sonny and Grady were at the table together, Grady said "so?", possibly meaning he wants to date Sonny, although Sonny replied with a "no". Grady finishes the sentence with "To friendship!".
Grady is usually goofy or silly but, he is very caring and compassionate. Grady mostly doesn't have a serious side but, he is serious and angry when Tawni and Sonny were late to rehearsals.
He is not very fond of the set's security guard, Murphy, who delights in tormenting the boys by tasting the pizzas they order. To get back at him, they buy a pizza and dump hot peppers on it; then, Grady delivers it under the guise of a pizza delivery boy. As they hoped, Murphy chomps down on the pizza and runs away screaming from the heat of the peppers. Upon finding out that Murphy went to the hospital, the boys visit him, and are at first led to believe he's dead. Murphy's still alive, however, and gets his revenge by making them eat spicy pizza. He said Sonny will return on his interview.
Grady has one brother, Grant, who screams, "Delta Nu!" in honor of his college fraternity of which he is the president.Grant is often rude to Grady and degrades him, but he is also protective of him and enjoys having him as brother.
Grady also has mentioned his dad who is in the military, which makes him move around a lot.
In "Sonny With a Grant," is it mentioned that Grady's grandmother is wealthy.