He is shown wearing an olive-colored pilot's jacket with the collar folded downwards, with a pastel gray shirt underneath. His legs are covered by tan jeans and black boots. To finish, he is wearing a brown aviator hat which covers his gray hair. His face is wrinkled and his skin is a light pastel brown which differentiates him from his cousin Greg Universe, although the two share similar noses.
Andy is a traditionalist, initially shown to be stubborn, judgmental, hot-tempered, and willing to hold a grudge. He is guarded and cautious in his attitude to the Gems, dismissing them as "hippies" because of their unusual appearance and lifestyle, and resistant to social change and deviations from the status quo in general. As he settles down and gets accustomed to the recent changes, however, he displays a lighter side, happily talking to Steven about his life as a pilot and ultimately allowing Lapis and Peridot to stay in his barn. Towards the end of his debut, he reveals that he is bitter due to his resistance to changes in his life, primarily how due to his family moving further and further away from him.
Steven was shocked to find out he had a relative he previously had no knowledge about, but immediately tried his best to befriend Andy despite his dismissal of Greg and the Gems. After agreeing to have a family dinner with Greg, Steven, and the Gems and finding his prejudices being challenged, Andy left the barn to Lapis and Peridot and took off in his airplane. When seeing this, Steven followed him in the air hanging from Lapis' arms and shouted out to him to talk him out of leaving. Steven explained that even though the Gems are his family, he needs contact with his human relatives as well, and was happy about getting a new member. Having grown attached to Steven, Andy saved him in his airplane from falling from a great height, and they agreed to stay in touch with each other.
Greg is Andy's cousin who used to come the family barn based on tradition. After Andy's debut into the modern timeline, the amount of things that changed and how Greg contributed to it led to some bitterness towards each other. It would eventually be resolved at the end of the episode.
Andy's relationship with the Gems starts off poorly. Upon meeting them in "Gem Harvest", he is infuriated with Peridot and Lapis for their modifications to the barn. He assumes them to be homeless hippies, and angrily demands that they leave his property. Andy is further upset when Greg informs him that the Gems are "aliens", interpreting this as illegal immigrants. The Gems are at first mistrustful of Andy, but, wanting to maintain possession of the barn and good relations with Steven's family, decide to make an effort to understand and befriend him. Despite their initial wariness, Andy and the Gems gradually warm up to each other over the course of the episode. The Gems are thankful for Andy for bringing them together, and he has seemingly come to accept the Gems as family, allowing them to stay at the barn.
- The name "DeMayo" is a spelling variation of "Di Maio", a surname found in Sicily and southern Italy.
- Andy's personality and conservative political views are based on common right-wing stereotypes.
- His mannerisms are also very similar to the character Carl from the show Aqua Teen Hunger Force who is voiced by the same voice actor. The most notable difference is Carl being a lot more foul-mouthed and nasty due to the adult nature of ATHF, as well as dressing more slovenly.
- Andy's surname, DeMayo, is similar to Nick Demayo's, an animation director for "Gem Harvest" as well as the series in general.
- Andy asks Steven to refer to him as "Uncle Andy" despite them being first cousins once removed. In certain cultures, referring to a distant relative as an aunt or uncle is seen as a sign of respect, while in others, it is a sign of affection.