Jello is a gelatinous dessert found on Earth that is made from a mixture of gelatin, sugar, and fruit flavoring, dissolved in hot water and chilled until firm. It is served in both the Atlantis mess hall and Stargate Command mess hall.
Dr. Rodney McKay is known to eat jello, preferring blue jello the most. Nola and Captain Samantha Carter are also known to have eaten blue jello. (SGA: "The Game", "Michael", SG1: "Urgo")
Teal'c once heard of a place on Earth where humans do battle in a ring of Jello, and suggested it to Colonel Jack O'Neill when they were bored. (SG1: "Ascension")
Lt. Colonel Cameron Mitchell is known to eat red Jello. Vala Mal Doran may also enjoy jello as she attempted to steal Lt. Colonel Mitchell's, though he was able to retrieve it before she had a chance to take a bite. (SG1: "The Powers That Be")