Sixteen - Season 1

The contestants are introduced and divided into two groups: Majors and Minors. This first group division is decided purely by JYP's A&R team, not Park Jin Young. The Majors are the members currently on track to debut in the new girl group and will be treated like true JYP stars, including living in a nice dorm, riding in a van, receiving pointers from current JYP stars, and practicing from 9 am to 9 pm. The Minors are to live like trainees in a dirty dorm and are disadvantaged by a 9 pm to 9 am practice time. The members of the Major and Minor groups will change as the contestants complete missions and show their skills. Once divided, Park Jin-young issued the girls the First Mission "Are you a STAR?" which challenged them to prove that they had star potential. Contestants could freely choose what they wanted to show, but JYP wanted to "see their ability to become a star or be able to feel that [they] are meant to be a star." During this mission, Park showed favor to those who thought outside of the box and showcased themselves rather than their talents, saying "It's great to have talents, but that talent must be yours. [...] I told you to show me why you are a star; I never said to show me that you can sing or dance." No one was eliminated in this episode.

Based on the performances seen in the first episode, Natty, Chae Ryeong, So Mi, Sana, and Ji Hyo replaced Momo, Ji Won, Mina, Min Young, and Na Yeon in the Majors line up, respectively. No one was eliminated based on the First Mission. The girls' next mission was "Album Jacket Cover," which challenged them to focus and produce high-quality photos in less-than-ideal conditions. Majors were allowed to shop for designers clothes for the photo shoot and decided on a dark, yet youthful vampire concept, while minors were sent to a street market and designed a fresh concept inspired by Wonder Girls. The results of the photo shoot exposed the strengths and weaknesses of the girls, revealing the natural charms of some and the struggles of others.

Due to their performance in the photoshoot mission, Mina, Tzu Yu and Jeong Yeon replaced Chae Yeong, Ji Hyo, and Da Hyun in the Major line up, respectively. Chaeyeon is eliminated from the competition because Park Jin Young observed that her inexperience and desire to do well obscured her natural charm and made her appear cold and stiff in the photos. However, he explains that this will be a good learning experience for her on her journey to stardom and concludes by telling her "you worked hard." The third mission, 1:1 Battle, is announced on results in Na Yeon and Chae Ryeong returning to Major status by replacing Tzu Yu and Sana. The results of the final match-up, between So Mi and Min Young, will not be revealed until the next episode. The final Major line up for this episode is Na Yeon, Chae Young, So Mi, Mina, Chae Ryeong, Natty, and Jeong Yeon. However, the battles involving So Mi, Min Young, Mina, Eun Suh, Chae Young, Ji Hyo, Momo, and Natty will air the next episode, leaving their final fates unknown this week.

The results of the remaining one-on-one battles are revealed. So Mi, Mina, and Natty remain Majors, while Min Young, Eun Suh, and Momo remain Minors. Ji Hyo replaces Chae Young in the Majors lineup, sending her to Minors. Eun Suh is eliminated from competition because she forgot her choreography in the middle of her stage. The contestants' next mission is to be a group challenge between minor and major teams. The teams are divided into Major A (Mina, Na Yeon, Chae Ryeong, Jeong Yeon), Major B (Natty, So Mi, Ji Hyo), Minor A (Momo, Ji Won, Chae Young), and Minor B (Tzu Yu, Min Young, Da Hyun, Sana). The match-ups are revealed to be Major A vs. Minor B and Major B vs. Minor A. The winning teams will make up the new Major lineup. The losing teams then will compete against each other. The losers of the second battle will be up for elimination. The girls are shown preparing for the competition, but no match-ups were shown this episode.

The girls prepare for their group battles, choosing performance outfits and rehearsing. The competition stage is held before a live studio audience, whose votes will determine the winners of each battle. Major A performed Pharrell's "Happy" against Minor B's performance of "Problem" by Ariana Grande. Major B hit the stage with Mark Ronson's smash hit "Uptown Funk" against Minor A's performance of "The Way You Love Me" by Keri Hilson. Based on audience votes, Major A loses to Minor B (189 points to 203 points). Tzu Yu, Min Young, Da Hyun, and Sana move up to the Majors lineup, while Mina, Na Yeon, Chae Ryeong, and Jeong Yeon fall to the Minors. Major B of Natty, So Mi, and Ji Hyo remain in the Majors lineup as they win against Minor A (202 points to 182 points). The losing teams, Major A and Minor A, will compete against each other; the losers of the second battle will be up for elimination. The results of the match-up will not be revealed until the next episode. The final Major line up for this episode is Tzu Yu, Min Young, Da Hyun, Sana, Natty, So Mi, and Ji Hyo.

For the loser's battle, Major A is renamed Minor A, and Minor A is renamed Minor B. Minor A (Na Yeon, Chae Ryeong, Mina, and Jeong Yeon) performed Lee Hyori's "U-Go-Girl" while Minor B (Chae Young, Ji Won, and Momo) chose Park Jin Young's "Swing Baby." Although JYP praised the performances of both groups, he and the audience both chose Minor A's performance as the winner (although the final decision was only based on the audience's vote). This placed Chae Young, Ji Won, and Momo in danger of elimination. In the end, Momo was eliminated because JYP felt that her flaws (being able to dance but not sing) were more obvious than Ji Won and Chae Young's during the stage. The Major lineup is asked by JYP to dance with him in an upcoming performance. While practicing with them, JYP gives the girls many tips about the dance and how to be successful dancers and performers. After the performance, the girls are taken to "Variety Camp," where the girls get a lesson in variety show charms from MCs Shin Bong Sun and Huh Kyung Hwan. In the previews for the next episode, it is revealed that the next elimination will be based on votes from the contestants themselves.

After completing Variety Camp, JYP gathers the girls together and announces that the mission will be member elections, where they will cast private votes on the Major and Minor line-ups. The results of the votes are revealed and Da Hyun, So Mi, and Natty are replaced by Na Yeon, Chae Young, and Jeong Yeon. However, JYP reveals there is no elimination for this mission. The girls are once again divided into four teams for their next mission, "Create Your Own Live Showcase." The teams will prepare a performance as well as be responsible for promoting the show. Major A (Ji Hyo, Chae Young, Min Young, Sana) prepared a slow, sexy version of Wonder Girls' "Nobody"; Major B (Na Yeon, Jeong Yeon, Tzu Yu) chose to perform miss A's "Hush"; Minor A (Da Hyun, Ji Won, Chae Ryeong) also chose to emulate Wonder Girls with "Tell Me"; finally, Minor B (Mina, So Mi, Natty) created a reinterpretation of JYP's "Who's Your Mama?". The song battles will be revealed in the next episode.

The girls rush through the streets of Seoul promoting the concert and handing out colored balls (Major A - Red; Major B - Yellow; Minor A - Green; Minor B - Blue). Before the show starts, attendees will place the ball in the correct group's bin to show which team did the best job promoting the show. The team that gets most of their balls back will be safe in the Major line up. After the performances, audience members are given white balls to vote for the performance they liked the best out of all four on their way out. This vote will determine the other members of the Major team. The girls are gathered by JYP to announce the results. He begins by explaining that the team he builds will not be based solely on talent but also on passion, as those with passion for what they do are the ones who are most successful. Ji Hyo, Sana, Min Young, and Chae Young are the first to make the Major lineup, with the greatest number of attendees (194) returning red balls. Before announcing the results of the audience's choice, JYP states that Major B's performance stood out to him the most, calling their performance an A+. The results of the public's choice and the next elimination will be announced in the next episode.

JYP reveals that Major A also ranked first within the audience votes, with Minor B in second, thus moving So Mi, Mina, and Natty up to Major and bumping Na Yeon, Jeong Yeon, and Tzu Yu down to Minor. In last place, Ji Won, Chae Ryeong, and Da Hyun were put in danger of elimination. JYP decides to eliminate Ji Won due to her off-beat dancing and unstable vocals while performing. JYP announces that the girls' last mission will be to become a real girl group onstage. He divides them into two group of six, but due to Minor lacking in numbers, they are given the advantage of choosing someone from the other team to perform with them. Although she will still be a part of Major, Ji Hyo is chosen to perform along the Minor team. JYP then gives the girls their new songs for the final mission's first round, explaining that teams were assigned songs that they would normally be bad at - the rhythmical "I Think I'm Crazy" for Major and the vocally-oriented "Truth" for Minor. He then reveals "Do It Again", which both groups will be performing in the final round and serves as a representation of Twice's musical direction. While preparing for the final mission, Major and Minor team are visited and mentored by miss A's Fei and 2PM's Jun. K respectively. After the performances, the girls receive praises from JYP, who chooses Minor as having given the better performance for the round.

The girls prepare for the final showcase, where the Major and Minor teams will perform "Do It Again" back to back. The teams spend one last night together reminiscing on their journey throughout the show, laughing at each other's silly moments, and sharing their heartaches and hopes. After the final performances, the girls receive praises from JYP. Chae Yeon, Eun Suh, Momo, and Ji Won join the final contestants on stage for a farewell performance before the results are announced. The finalists are gathered on stage where the Major team turns in their necklaces. Na Yeon, Jeong Yeon, and Da Hyun take the place of Natty, So Mi, and Min Young in Major lineup, respectively, thus eliminating them alongside Tzu Yu and Chae Ryeong. JYP then throws in a twist, announcing that Twice will be a nine-member group. Along with the current Major line up (Na Yeon, Ji Hyo, Mina, Da Hyun, Jeong Yeon, Chae Young, and Sana), he chooses Tzu Yu to join. JYP then surprises the contestants and the audience by announcing that Momo, who was eliminated in the fourth mission, will be the final member of Twice. Tzu Yu is added from audience's opinion through online voting and Momo from the A&R Team and the Trainers' decision. The group's final line up is: Na Yeon, Jeong Yeon, Momo, Sana, Ji Hyo, Mina, Da Hyun, Chae Young, and Tzu Yu.