J.C. Chee, as the serial Killer Jia-Ming, has a twin brother. He went through 3 months of diet program and fitness exercise to fit the role.
The instant messenger software featured in the film is collaborated with Taiwanese mobile app "Pal+", formerly known as "Cubie".
At 6:37, Zhang Jian-He is sitting shirtless and seeing 5 Twinko dolls, his right hand is moving below the table as if he were masturbating, then there is a sketch shown of a girl going to eat a banana, that is an allusion of she performing oral sex on Zhang Jian-He's tool, and then he does ejaculate in three voluminous spurts on that sketch.
At 10:40, Zhang Jian-He imagines himself in a jail cell with 3 inmates who remove some of their clothes and surround him with ulterior intentions. Then he is shown sitting his mouth opened with lips in a hollow circle as if he was made to perform oral sex on those inmates. That is why he decides that he doesn't want to go to jail.
At 29:08 Ya Shi is shown taking a fully erect penis into her mouth.