Hayley Dreamsmasher Smith is the eldest child of Stan and Francine Smith. Hayley, age 19, has a younger brother, Steve. They reside in Langley Falls, Virginia. The family also has a fish named Klaus and a boarder, a space alien named Roger. Hayley's maternal grandparents are Bah Bah Ling and Ma Ma Ling. Jack Smith is Hayley's paternal grandfather. Her paternal grandmother is Betty Smith.

Hayley Smith’s appearance on the show is constant. Hayley stands at a short height of 5’3". Hayley has long, black hair that just passes her shoulders in length. In “Blonde Ambition” Hayley dyes her hair blonde, and in “Stan Knows Best” she dyed her hair green, although it is short lived, as Stan eventually shaves her head that night. She has a normal build in terms of weight, slightly on the thinner side. She sports a gray tank top, blue flare jeans, and a magenta and green headband. Her outfit is a sort of riff on the stereotypical outfit of that of a 1970s hippie. She also dons a silver, peace-sign necklace, silver bangle arm-bands/gauntlets. She possesses decently big feet, as evident from her having significantly larger feet than her taller mother. Hayley mostly only rocks Arizona-style sandals, if not barefoot that is. Her feet appear significantly smaller if she isn’t wearing her jeans.