Wait 'Til You're Older (2005)
Andy Lau Tak-Wah co-stars with Karen Mok Man-Wai in this odd family fantasy film directed, produced, and co-written by Teddy Chen Tak-Sum, who gave us the films Downtown Torpedoes (1997) and Purple Storm (1999). Screenplay co-written by producer Cheung Chi-Gwong and Susan Chan Suk-Yin borrows a basic premise from the Hollywood movie Big and infuses it with a decidedly Hong Kong flavor.
Kwong has a troubled home life and is goofed on by classmates at school. He has a crush on his teacher (Cherrie Ying Choi-Yi) and hates his stepmother (Mok) but is too young to understand his father's personal struggles. He wishes he could be a grown-up and straighten out his world. He gets his hands on a magic potion and wakes up as Andy Lau. He, of course, begins to see everything differently and most of it is not so good. The scenario goes through some dark, adult places and manages to jerk some tears when the filmmakers keep a child-like point of view on the proceedings.