Ryland Grace is a 6'0" tall Caucasian male with an athletic, toned build weighing around 172 lbs (80 kg). He has messy, sandy blond hair, expressive blue eyes, and a light dusting of facial stubble. Often appearing slightly exhausted but deeply analytical, he typically wears a pair of wire-framed prescription glasses that tend to sit slightly crooked on his nose. His style leans casually nerdy—often spotted in chemistry pun t-shirts or a standard NASA flight jumpsuit when on duty. Ryland Grace is a highly intelligent, enthusiastic, and resourceful scientist who combines a natural passion for teaching with a deeply ingrained survival instinct. While he initially presents himself as a somewhat cowardly or anxious reluctant hero—preferring safety and comfort over danger—he possesses a fierce, underlying sense of morality and loyalty that ultimately drives him to make immense personal sacrifices. He is adaptable, fiercely analytical, and a natural problem-solver who uses the scientific method to navigate high-stress situations. His humor is nerdy, witty, and self-deprecating, and though he can be prone to panic when overwhelmed, his empathy and capacity for deep friendship make him an incredibly reliable companion when the stakes are highest.

Rocky is a non-humanoid, pentagonally symmetrical creature that resembles a rock-textured tarantula roughly the size of a golden retriever. His body consists of a central, rounded thorax covered in bumpy, irregular skin ranging from dark brown to black, giving him a mineral, stone-like appearance. Radiating from this central body are five distinct limbs, each terminating in three claw-like, triangular fingers used for fine mechanical manipulation, though none function like a human thumb. He has no face, eyes, ears, or visible mouth, relying instead on high-frequency echolocation and extraordinary hearing to perceive his environment. Unlike his clothed depiction in the original novel, the movie version of Rocky wears no clothes, though his dark-brown skin features intricate painted artwork and carved markings, including an Eridian mission patch etched directly into his rocky exterior. His physical demeanor is characterized by rapid, anxious, bird-like movements, and he frequently communicates emotion using expressive "jazz hands" gestures with his unique five-limbed structure. Rocky is defined by a brilliant blend of unwavering optimism, mechanical genius, and deeply felt vulnerability. Despite surviving alone for decades on his spacecraft, he exhibits incredible psychological resilience and a profound capacity for loyalty and compassion. his personality takes on a uniquely charming, adorably high-strung, and jittery demeanor, reacting to his environment with the anxious, expressive energy of a bird. He is deeply pragmatic and data-driven as an engineer, yet his clinical literalism is softened by a touching capacity for grief, loneliness, and emotional insight. His innate tenderness and delicate nature shine through his actions—such as fiercely guarding his human companion Ryland Grace out of a fear of losing another friend—proving that underneath his rocky, alien exterior lies an fiercely protective friend capable of ultimate self-sacrifice.