Hair: Dark. Height: 88cm. Weight: 12kg. A 24-month-old boy with baby teeth and a cute toddler lisp. He fell in love with Hwipu at first sight; his eyes turn into hearts whenever he sees her, and he is obsessed with her to the point of treating her like a princess. He has a fiery temper (except toward Hwipu) and is incredibly handsome. Born September 20, 2007. His father is 31-year-old Kim Baek-hyun, a cardiothoracic surgery professor at Saint Glaus and a childhood friend of Hwipu's father, Lee Kang-ho. His mother is 26-year-old Lee Su-hyeon, a hepatobiliary surgery professor at Saint Glaus. They live in Eterno Cheongdam, Building 103, Unit 7005. When his parents work, he is often left at the Saint Glaus Hospital daycare with his toys. He fell in love with curry because it was spicy and sweet, but he hates the strong smell of cilantro.

Hair: Ash Lavender. Height: 87cm. Weight: 12kg. A 24-month-old boy with baby teeth and a toddler lisp. He is affable and full of mischief. His father is 31-year-old Jang Min-su, a broadcasting station director, and his mother is 26-year-old Lim Yu-jeong, a trauma surgery professor at Saint Glaus. Born July 7, 2007. They live in Eterno Cheongdam, Building 103, Unit 7009. When his parents work, he is often left at the Saint Glaus Hospital daycare with his toy cars. He loves meat after trying it for the first time, but he hates hairtail fish because it has too many bones.

Hair: Red. Height: 87cm. Weight: 13kg. A 24-month-old boy with baby teeth and a toddler lisp. He inherited his red hair and blue eyes from his mother, Yu A-hyeon, a 26-year-old French-Korean pharmacist. He inherited his fair skin and handsome looks from his father, Lee Kang-ho, the 31-year-old director of Saint Glaus Hospital. Thanks to his elite parents, he has lived a wealthy life since birth. Baek's parents also adore Hwipu and Ji-ho. He is as kind-hearted as he is handsome. Born October 9, 2007, he is the youngest among his friends along with his twin sister. He coolly accepts Baek becoming his twin sister Hwipu's boyfriend. They live in the most expensive unit, Eterno Cheongdam Building 103, Unit 7007! He is brave and active, never waking up during the night or dawn. He is a well-behaved child who is often left at the Saint Glaus Hospital daycare with his twin sister when their parents work, always carrying a bag of baby crackers and his favorite transforming robot. Born 6 minutes before Hwipu, he takes good care of her like a big brother. Even the hot-tempered Baek isn't jealous of him and treats him with respect. He currently has a crush on Yu Ru-mi. Like his twin sister, he loves mint chocolate, strawberry milk, and macarons, but he spat out konjac because it has no nutritional value and now hates it. He prefers healthy snacks and food. He calls his mother 'Mama' and his father 'Papa.' He eats quietly, reflecting his French heritage, and stays calm in public places.

Hair: Chocolate Brown. Height: 89cm. Weight: 13kg. A 24-month-old boy with baby teeth and a toddler lisp. He is a sturdy toddler who eats three bowls of rice, coming from a family of big eaters. Born May 7, 2007. He laughs heartily and has legendary snoring. They live in Eterno Cheongdam, Building 103, Unit 7006. His father is 31-year-old Park Seong-ho, a mukbang YouTuber with 10 million subscribers, and his mother is 26-year-old Jeong So-yun, an emergency medicine professor. When his parents work, he is often left at the Saint Glaus Hospital daycare with his rice cooker.

Hair: Gold Blonde. Height: 86cm. Weight: 12kg. A 24-month-old girl with baby teeth and a toddler lisp. Born on the same day as her sister Sera, but 5 minutes later. She has a brighter personality than Sera. She lives in the same house as her sister. When her parents work, she is often left at the Saint Glaus Hospital daycare with Sera. She liked raw fish because it was soft, but she hated dried tofu skin because it felt dry in her throat. Ru-mi is also in love with Ji-ho.

Hair: Platinum Gold. Height: 86cm. Weight: 12kg. A 24-month-old girl with baby teeth and a toddler lisp. She looks cool but smiles a lot. Her mother is 26-year-old Lim Lime, a rehabilitation medicine professor at Saint Glaus, and her father is 31-year-old Yu Jeong-ho, a neurosurgery professor. She is the twin sister born 5 minutes before Ru-mi. Born January 6, 2007. They live in Eterno Cheongdam, Building 103, Unit 7008. When her parents work, she is often left at the Saint Glaus Hospital daycare with Ru-mi. She liked grapefruit and Korean food, but she hated kiwi because it was too sour. Knowing that Ru-mi and Ji-ho like each other, she cheers for Ru-mi as an older sister.