First of all, we can't deny the reason for the foil, especially when Lao Xing was denounced by Xiao Liu. The audience will be more emotionally inclined to Lao Xing, and they will feel as if Lao Xing can be tolerated more. In fact, if there is only Lao Xing or Xiao Liu in life, everyone will only find it annoying. Only when there is a comparison can we win or lose.

The second is the hidden meaning of these shortcomings. The combination of the shortcomings of Primary Six will give people a feeling of "I don't want to play with him because he is terrible like a time bomb". Because of the coexistence of so many shortcomings, many actions based on this will make things very bad. Such a person can easily hurt people physically and emotionally. Animal instinct is to seek advantages and avoid disadvantages.

Third, proper limit of Lao Xing is taller than Xiao Liu, because he is older and has more life experience. When Lao Xing was young, he was estimated to be similar to Xiao Liu.

To sum up, the dramatic identity exchange gives Lao Xing a point of sympathy, and the perennial sophistication adds a point of emotional intelligence to Lao Xing, which can cause less harm and add a point of security to Lao Xing. Generally speaking, the audience will think that the role of Lao Xing is better than that of Xiao Liu.