The only person in the amusement park who knew about acting was probably Lou Xiaobao. Although Zhou Yu claimed to be a director, the real director was Ling Daoran, so Lou Xiaobao was the only one who could give some acting guidance to those who would be recruited next.
Although Zhou Yu said that it was a privately-made movie, he didn't want to really make a third-rate movie. After all, Little Muli and the other children of his were looking forward to it. In addition, director Ling Daoran had an 'obsessive-compulsive disorder'. It would be very hard for him to accept bad acting skills.
After Xiaobao joined in, Zhou Yu needed to recruit some other supporting roles.