Grace is a hallucination of a female Tau'ri child who was seen by Major Samantha Carter after receiving a head injury when trying to get the Prometheus to make a small hyperspace jump into a gas cloud. A hallucination of Dr. Daniel Jackson (who was part of Carter's subconscious) believed her to be the physical personification of the entity he believed the gas cloud to be. Grace hauntingly sang "Twinkle Twinkle Little Star." (SG1: "Grace")