- Fromis_9 was formed on her birthday (September 29, 2017)
- Her childhood nickname is Song A-Ji (puppy) and In Idol School, her nickname was Mal-Babo (because she can’t talk properly), she also has the nickname HaBBang.
- Despite her youthful looks, she initially struggled with a cute and innocent concept for Like Ooh-Aah by Twice because she was in a hip-hop dance club in high school.
- She is good at hip hop dances, but poor at rapping.
- She was ranked no.3 in singing Into The New World by SNSD in initial vocal assessment and no.2 overall in physical endurance.
- She did poorly in dance assessment because she couldn't grasp choreography quickly, but was good at freestyle dances.
- By 2023, she is the de-facto leader in dance practices.
- She studied hapkido briefly, but only got an S-board because the course was too short to gain a belt.
- She can kick vertically with either leg.
- She was the only member who could make Dalgona and cotton candy, but during Fromis' Room, she burnt her hand during a fundraising night, so she had to leave early.
- Despite her being clumsy, she successfully became Jisun's Sous Chef in Fromis' Room.
- She can debone chicken both with kitchen scissors and her bare hands without Jisun's help.
- She cares about her birthday so much that she'd start counting down as far as a year before her next birthday, meaning as soon as she has her birthday, her countdown restarts the day after.
- She later gained the nickname "Song Duckling" to match Yena of IZ*One as they share the same birthday, but Hayoung is older by 2 years.
- She tends to open her mouth while dancing to let more air in.
- She is the main harmonizer for the group, even when they are doing karaoke in variety shows.
- She also tends to scratch her nose when her bangs become too long and makes her nose itch.
- According to the group's third appearance in Fact in Star: She is poor at finding camera and spotting "landmarks" in a filming set, since her main focus in high school was dancing, unlike Chaeyoung and Jiheon, who studied Performance Arts, which includes acting and directing.
- She dislikes winter and cold weather.
- However: During summer, she likes chewing ice with her iced drinks.
- Her friends always think of bangs when thinking of her, so she promised that she will try different hairstyle in the future.
- Her favorite music genre is acoustic. (V LIVE)
- She composed her first song at 9 years old. The song is about blankets.
- Her looks make her look younger than her actual age.
- She thinks her charming point is her skin.
- Her MBTI is tested as INFP (Mediator, Fi-Ne-Si-Te), it was further confirmed on ep. 23 in season 3 of Channel_9.
- On her 19th birthday in 2019, she got angry over the trivial matter of the origin of food as they were in Indonesia, but Jiheon added fuel to the prank.
- She cries the easiest in the group, but cried tears of joy when the group finally won their first no.1.
- She is good at making animals by shredding papers.
- She inherited her artistic skills from her grandfather, who was an artist.
- She loves to cook but the other members doubted it, even though she’s good at it. Hence she sometimes become Jisun's Sous Chef.
- She is also an intuitive cook, measuring by estimation, and making boneless chicken without prior knowledge and having Jisun being there to teach her. Her motto: "When it coes to cooking, the order is important, of course, but I think the ingredients matter the most... ...but it's also all about speed"
- Her favorite foods are cheese sweet potato burrito, bone soup, and beef.
- She is good at catching shoes with a large basket
- She can also catch a roll of tissue paper with a toy light sabre
- She has a habit of sniffing to know the aroma of soap or beauty products.
- She has a flexible body so can do the splits.
- She also has great sense of regaining balance. She can play the guitar and eat while staying on a Swiss ball.
- She also can do a backwards standing long jump. Her best record was 90cm.
- She can do a handstand and headstand without support.
- She can impersonate an opera singer suddenly having voice of a monkey when she sings in high notes.
- She can also mimic crow's call.
- She has a Yoga Instructor License. She also had Aerial Yoga Instructor License, but it expired.
- Even though Hayoung likes Hip-Hop she's not good at rapping.
- Unnies Line (Saerom, Hayoung, and Gyuri) cry the most and also cry easily. (V LIVE)
- Hayoung says that she wants to develop her composing and singing.
- All the members love teasing Hayoung, but are often stunned and impressed when she is doing things that she is good at, like being in high places, doing Yoga, balancing on a Swiss ball and shredding paper to make art.
- She made many errors when speaking Korean because speaks with a lisp.
- It takes her a long time to string together sentences, so the job of introducing songs and albums for music shows are often done by Jisun, Jiwon, Gyuri and Saerom. Saerom, however, also isn't good at memorizing the introduction, either.
- She is the only member who is very comfortable with heights.
- She also likes setting obstacle courses for other members.
- Her usual pose on camera is to put up a sideways peace sign in front of one of her eyes.
- She often makes other members make acrostic poems on the spot.
- She is only good at spinning a hula hoop without moving.
- According to Fromisoda #44: Her guitar is Crafter SRP G-27ce. Despite the English name, it's a Korean brand.
- She also has a guitar without the headboard and soundhole to reduce volume.
- Her wake-up and goodnight calls for Flover are in the style of military drill sergeants, that's despite her not coming from a military family like Gyuri does.
- She sang the high note adlibs on DM, reaching A6 even on the chant guide.
- As a vice-captain, she leads the team in warmup exercises, but only Seoyeon follows along.
- If she wasn't in the entertainment industry, she wanted to become a zookeeper.
- She is extremely competitive and perfectionistic. When she falls and makes physical mistakes, it makes her more relatable to .
- She is also a good luck charm, as she always leads her team to victory.
- In season 3 of Channel_9, she had won 7 of 9 competitive games either individually or as a member of her group heading into the 1 vs.8 handicap game.
- On the 1 vs. 8 handicap game:
- She easily beat all members to wear the most items of clothing.
- She managed to capture herself and Nakko in more photos than 98-Line.
- She did the following 3 tasks on her own against three different members:
- She can peel the plastic film off peppermint lozenges with mittens on vs. Seoyeon.
- She can drink Powerade with a 2m straw quickly vs. Nagyung.
- She can pull a trolley with water by only using her toes vs. Chaeyoung.
- She can thread a needle through a pin hole while standing on a vibrating exercise machine vs. Jiheon and Jiwon.
- Her ranking of competitiveness:
- Herself
- Nagyung (for persistence and strategic mind)
- Chaeyoung
- Jiwon (for effort rather than actual skills to win)
- Jisun
- Gyuri
- Saerom
- Seoyeon & Jiheon (both dislikes physical exertion, but Jiheon is better than Hayoung at reading and tongue-twisters.)
- Hayoung's lowest point after debut was in 2020 while preparing for Feel Good because fans weren't allowed to attend live recordings due to COVID-19. It was also their comeback after a gap of over 14 months.
- Hayoung is the first member to sing a Japanese cover for Flaylist in 2022. She was meant to play the guitar while singing but decided against it after rehearsals.
- She can read Saerom's lips, pronounce incorrectly, but fix her mistakes as say the correct answer before Saerom finishes the question.
- She dislikes wearing skimpy swimwear, going as far as wearing a wet suit just to swim in a shallow pool, even though she is an OK swimmer.
- While she doesn't have the worst eyesight in the group, her prescription glasses suggest that it's bad enough.