During filming, 'Spacked Out' completely abandoned the original script written by Shiu Lin Au, Laoshu, and Sin Ling Yeung because it only magnified the darkness and downfall of teenagers' problems without caring about their inner feelings and hopes for the entire social environment. Therefore, director Lawrence Ah-Mon, assistant director Andy Tse, and art director Wing-Gei Chan recreated the script during filming. Only the characters Sissy and Bean Curd were originally described in the script by screenwriters Laoshu and Sin Ling Yeung. The rest of the plot did not use any of their creations. Some of the plot in the film was even provided by the actors during filming. Most of the dialogue was improvised by the actors themselves because no one could write their conversations.
Tam Kit-Man (Debbie Tam) grew up in Hong Kong and never received any formal training in drama. At the age of 13, she and her friend Chun Wai Li were discovered by director Lawrence Ah-Mon on the streets of Tuen Mun and were invited to audition for the film "Spacked Out." Debbie stood out among hundreds of the participants at Milkyway Image and won a film acting contract, playing the role of Cookie in the film "Spacked Out" (2000). Her friend Chun Wai Li was eliminated in the first round of auditions. During filming, the director added more scenes for her to perform due to her excellent improvisational performance, making her the first female lead in "Spacked Out." This started her film career, and Debbie was also nominated for Best New Performer at the Taipei Golden Horse Film Festival for her role in "Spacked Out".
Maggie Poon (Mei Kei Poon), who played the role of 'Bean Curd' in the movie, had no previous experience in filming. Originally, she only accompanied her classmates to audition at Milky Way Image. She did not participate in the audition, but a staff member saw her and took her phone number and took a few photos for record. However, director Lawrence Ah-Mon gave up on her in the first round of interviews because he felt that she looked too much like a doll and not like an ordinary person, so Maggie was not originally among the main cast. But assistant director Andy Tse met Maggie before filming 'Spacked Out' when he shot an advertisement. She performed very well as a rebellious girl. Andy Tse showed the advertisement to the director, and Lawrence Ah-Mon agreed with her performance and cast Maggie as the character 'Bean Curd'.
Yiu-Fai Lai, the Director of Photography for 'Spacked Out', was an up-and-coming cinematographer in 2000 and had already shot several films. He had previously worked as a cinematography assistant for Christopher Doyle and participated in director Wong Kar Wai's films 'Chungking Express' and 'Happy Together'. Yiu-Fai Lai attached great importance to this opportunity to shoot 'Spacked Out' and brought in his partner Ho Po-Wing to participate in the film as a Focus Puller. They met director Lawrence Ah-Mon's requirement to use many hardheads to create a realistic style. 'Spacked Out' was a test for him.
Before the start of filming for 'Spacked Out', Director of Photography Yiu-Fai Lai brought in Wong Kar Wai's lighting director, Wong Chi-Ming, to take on the role. Wong Chi-Ming had already served as lighting director for films such as 'As Tears Go By', 'Chungking Express', 'Fallen Angels', and 'Happy Together'. He was originally a very expensive lighting director, and basically, the budget for 'Spacked Out' could not afford him. However, Wong Chi-Ming wanted to support Yiu-Fai Lai in taking an important step and reduced his own salary to join the crew for the sake of friendship. As a result, the visual and lighting coordination of 'Spacked Out' was more refined compared to films of similar cost at the time. Therefore, Wong Chi-Ming, Yiu-Fai Lai, and Ho Po-Wing were very important contributors to 'Spacked Out'.