Previously, one SM insider stated about the members' selection process for an idol group, "We mix children who are completely different. Beginning with the visual member, there is a member for MC-ing, a member for dancing, a member for singing, etc. Because the members' popularity will always change. Which is why Girls' Generation can be considered a platform of sorts. In terms of group numbers, an odd number is best because it allows one member in the center."
About the selected trainees' backgrounds, it was revealed, "In the past, we had a lot of children from lower class families join, but nowadays it's children from all social classes. Everyone is a candidate now. Considering their circumstances, we have them go through heavy dental work. Visuals are always something we can work with, but height can be problematic. The trainee period has become around 4-5 years, during which we provide fixed education. Because if they fail at becoming an idol, we cannot guarantee their futures. They learn everything from dance to foreign language. They are very competitive in these fields. Only the smart ones survive."
Chief of SM's music producing team, Lee Sung Soo, previously gave some insight into the selection process for which songs go to which group. "We receive about 100 songs a week. Each of these songs are graded by their demos. After that process, Lee Soo Man chief producer chooses which songs will become title songs." According to Lee Sung Soo, it took approximately a month for him and Lee Soo Man to adjust the instrumentals, the melody, breathing, lyrics, and more to TaeTiSeo's "Twinkle".
Insiders also stated that people who used to be idol trainees get scammed easily, because they are used to other people doing the work for them, and are susceptible to the urgings of those around them.
Many netizens, after seeing the past interviews come to light, expressed their respects for idol trainees who managed to debut successfully in big name SM groups, particularly Girls' Generation, saying, "Girls' Generation are seriously amazing people", "Artists who managed to debut are really special", "This is kinda sad", "Idols really need good people around them or need to have really strong mentalities to survive", and more.