Leeteuk asked Kyumin to choose the first mom and Kyumin chose Hyorin's photo with his toe.
Leeteuk chose Soyou as second mom after he looked at all of the moms' diaries for Kyumin.
Since Bora was absent due to filming Invincible Youth 2, the Sistar moms did a calligraphy contest and Dasom became the one-day mom for Kyumin.
Leeteuk chose Bora because she became the winner of 3 different missions.
In episode 9 and the early parts of episode 10, Bora could not participate in Hello Baby's recording because she was filming for Invincible Youth season 2, so Leeteuk made a competition to pick the mom for a day which Dasom won.
Leeteuk and Sistar took care of a thirteen-month-old baby boy named Kim Kyumin who liked Pororo but hated ducks. In the first episode, Kyumin cried when he heard a duck's quack but would dance when he heard music.
Hello Baby season four is similar to that of Leeteuk’s ‘Find Mom’ project. It shows the process of finding the favorite mom amongst the four Sistar members. Unlike the past seasons, it was the baby who was leading the shows, not the parents.
Super Junior's leader Leeteuk was chosen as the dad and was the first one to meet Kyumin. He did not know anything about babies and made Kyumin cry a lot; but after a while, he went to Sistar's dorm and asked them to be Kyumin's moms. Leeteuk gave a mission to Sistar to make a Hello Baby diary about Kyumin.
9 September 2011
Kyumin picked his first mom, Hyorin. The Sistar members and Kyumin went to support Hyorin at the Immortal Song recording at KBS Studio. Leeteuk and Kyumin looked for a baby house while Sistar competed for baby necessities.
16 September 2011
In a continuation of last week's episode, Sistar still competed. Leeteuk and Kyumin found a house and Leeteuk tried to change Kyumin's diaper. Sistar and Leeteuk planned a housewarming party and invited several idols. Kyumin went to his first photo shoot with Sistar and Leeteuk to make his portfolio.
23 September 2011
In a continuation of last week's episode, Sistar and Leeteuk worked hard to make Kyumin smile in the photo shoot. Leeteuk bought family shirts for himself, Hyorin and Kyumin and then took a family picture along with the Sistar aunts. Leeteuk checked Sistar's Hello Baby diaries and picked Soyou as the second mom. Leeteuk gave Soyou a mission to bring Kyumin to the hospital to get a vaccine and decorate Kyumin's room. Also, Sistar took Kyumin to his first audition.
30 September 2011
Leeteuk and Sistar sent out invitations to their housewarming party. Leeteuk bought a family picture and pop-art portrait for the baby house. Leeteuk's elder sister came to the house and surprised the Sistar moms.
7 October 2011
At a housewarming party, Soyou and Leeteuk got couple PJs from Ju Ri. Guests helped Sistar and Leeteuk clean the baby house. Girl's Day came as guests for Hello Baby's housewarming party for Leeteuk. For Sistar member Bora, Leeteuk called Song Joongki (Hangul: 송중기) because he was her ideal type and he invited Girl's Day, who were not Sistar's favorite people. Sistar and Leeteuk asked guests to write lyrics about Hello Baby for the family song. Leeteuk gave Soyou a present.
14 October 2011
Sistar and Kyumin went to Leeteuk's radio show Super Junior's Kiss The Radio. Sistar gave a mission for Leeteuk to go on a date with Kyumin and capture Kyumin's expressions of happiness, anger, sadness and joyfulness on camera. Leeteuk took Kyumin to Seaworld. To pick the third mom, Leeteuk gave three different missions to Sistar. The first mission was on stage, the second was a trivia quiz about Kyumin, and the third was a popularity vote by the people. Bora won and became the third mom.
21 October 2011
The Hello Baby family went on a picnic as a wish from Bora. Sistar made a hidden camera for Leeteuk. Leeteuk bought a couple of jackets and rings for Bora.
28 October 2011
Bora could not attend Hello Baby's recording so Leeteuk chose a mom for a day through a calligraphy mission. Dasom won and became the mom for a day. When Dasom and Leeteuk were bathing Kyumin, Kyumin accidentally went under the water. Sistar and Leeteuk took Kyumin to his first photo-shoot for an organic cosmetic CF. Soyou wanted to give a congratulatory cake for Kyumin's first ad, but ended up with a mess. The Hello Baby family went to the amusement park as Dasom's wish.
4 November 2011
The Hello Baby family went to Lotte World. Hyorin, Soyou and Leeteuk made a hidden camera for Dasom to see how much she loved Kyumin. Bora mom came back and went on a date with Kyumin to Sunflower Garden Experiences to invigorate Kyumin's five senses. Bora and Kyumin went to a pottery studio to make a gift for Leeteuk.
11 November 2011
The Hello Baby family made kimchi for winter with Kim Bo-min's help. Sistar, Leeteuk and Kyumin recorded the family song. The lyrics were combined from the ideas of the guests who had attended the housewarming party. DK made the music come to life by helping them record it.
18 November 2011
Kyumin held his first fan meeting. Leeteuk make a special narration about Kyumin and Sistar. The Hello Baby family revealed their family song; Leeteuk made the title "For Kyumin". Even though a lot of singers participated to make the lyrics, Leeteuk choose 90% of them from Girl's Day's ideas. After the fan meeting, they had a long and tearful goodbye with Kyumin.