A 2002 Hong Kong Supernatural Martial Arts action movie, starring Cantopop starlets Gillian Chung and Charlene Choi (Twins) as vampire slayers as well as Hong Kong superstar singer Ekin Cheng and Edison Chen.
Reeve (Ekin Cheng) is the best of the best when it comes to slaying the vampires infesting Hong Kong. He's tasked with training Gypsy (Gillian Chung) a novice slayer, who's more interested in fangirling him than concentrating on her training. Reeve's Tsundere sister, Helen (Charlene Choi), attracts the attention of Prince Razaf (Edison Chen), a "sentimental" vampire who refuses to drink blood. Meanwhile, a European vampire, the Duke (Mickey Hardt), is on a quest for the magical stones that will unlock a supreme power....
Features an extended cameo by Jackie Chan, who ended up on the DVD cover of some foreign editions.
Followed up by The Twins Effect 2 in 2004, a fantasy sequel In Name Only marking the debut of Jackie Chan's son.
The Twins Effect provides examples of the following tropes:
- Action Girl: Both Gypsy and Helen.
- Aristocrats Are Evil: The Duke.
- Badass Bystander: Jackie Chan plays a random ambulance driver who is skilled enough in martial arts to be able to fight multiple vampires and win despite having no idea what vampires are or even that they exist.
- Badass Longcoat
- Chekhov's Gun: Razaf's alleged love for bananas.
- Chop Sockey: Even includes a fight scene with Jackie Chan versus biker vampires!
- Chinese Vampire: Strangely, averted. Reeve mentions that there aren't usually many European vampires in Hong Kong, but almost every vampire in the movie is Caucasian. It's worth noting that the Chinese vampires we do see, such as Razaf and Prada, don't seem very different from the Duke and his cronies.
- Combat Stilettos: Averted. The female characters all wear reasonably practical-looking boots when fighting.
- Covers Always Lie: The Korean DVD Cover◊ makes the film look like an intense thriller focusing on Jackie Chan and Ekin Cheng.
- Distressed Damsel: Prince Razaf
- Dogged Nice Guy: Prince Razaf, unusually for a vampire romantic hero, wins Helen by being sweet and sincere, not with dangerous sex appeal.
- Elevator Escape: Helen pushes Razaf (who is weak from lack of blood) into an elevator and turns to face their vampire pursuer. She's almost killed before Razaf pushes the 'Doors Open' button and pulls her inside with him.
- Fangirl: Gypsy for Reeve.
- Girl Meets Vampire Prince: Helen and Razaf's love is complicated by the fact that her brother is the most accomplished vampire slayer in the world, and he's a vampire prince. His sidekick Prada advises him to take up with a vampire woman to offset the Carnivore Confusion that will inevitably result.
- Impaled with Extreme Prejudice: Duke by the combination of Helen and Gypsy.
- Improvised Weapon: A paramedic (played by Jackie Chan) force-feeds a pair of vampires some pills from his ambulance so they'll be too busy tripping out to continue to pursue him or the protagonists.
- Kryptonite-Proof Suit
- Manic Pixie Dream Girl: Helen has elements of this paired with her Tsundere-ness.
- Market-Based Title: Released as Vampire Effect in America, likely because most Americans would not be familiar with the Twins, who do not play Twins in the film.
- Merchandise-Driven: The film was pretty much made to cash in on the popularity of the Twins, among other artists associated with Emperor Entertainment Group.
- Non-Actor Vehicle
- Shoe Slap: In the final battle, Helen momentarily stops Dekotes... by kicking her shoe into his face.
- Staking the Loved One: Gypsy taking out Reeve.
- Tsundere: Helen.
- "Uh-Oh" Eyes: The eyes of vampires glow bluer the more powerful they get. Gypsy's eyes go black when she swallows some of the magical energy that transforms her into a 'semi-vampire'.
- Vampires Are Sex Gods: Mostly averted. Prince Razaf spends a great deal of time and energy wooing Helen.
- Vampire Hunter: Reeve and Gypsy. By the end, Gypsy, Helen, and Razaf.
- Vegetarian Vampire: Razaf lives off blood-wine sent to him by his father, the vampire king, and refuses to attack humans.
- Wolverine Publicity: Jackie Chan appears prominently on the covers of both the US and Korean editions of the DVD. His appearance is actually just a small cameo.