Buck Grunt is the youngest son of General Buzz and the late Lyla. He has two older brothers, Ripp and Tank. Studious and smart, Buck is serious but also nice, and has an A+ in school when the game begins. Buck is the nicest member of the Grunt household, with 9 nice points. He also has a good relationship with his acquaintance Jill Smith, despite the feud between his family and hers.
Overall, he gets along with his family, but is somewhat distant from Tank and General Buzz. According to his bio, his accomplishments are largely ignored by his father. He is overweight when the family is first played, and is 4 days away from becoming a teenager. He wants to be a pet stylist to the stars, although there is no such career or level in any job.
While he has blue eyes, he has a recessive gene for grey eyes.
He has short blond hair. He wears a red t-shirt over a yellow long-sleeved shirt, with brown shorts and sandals. He has the same clothing and hair color as Strangetown townie Samuel Riley.
In The Sims 2 for PSP, his father and brothers make an appearance, yet Buck does not. The reason for this is unknown.
Like Jill Smith, Buck has a hidden Popularity Aspiration token which can be viewed in SimPE. Other pre-made toddlers and children have this quirk, though these childrens' aspirations can be changed when they become teens.