Kung Fu Hustle Batterflies

The housing arrangement of the Pig Sty Alley is similar to that of a 1973 Hong Kong film, The House of 72 Tenants (七十二家房客)

When Sing arrives at Pig Sty Alley, he shows fancy footwork with a football, then says, "You're still playing football?". This refers to his previous movie, Shaolin Soccer as does the scene where a Clerk beats Sing up on a bus. The clerk also appeared in Shaolin Soccer as the leader of an opposing team who used hidden weapons to beat up the Shaolin Soccer team.

In the scene were he robs the Ice Cream stand, a poster for the 1935 movie Top Hat is in the background

As Sing arrives at the door to the Beast's cell in the mental asylum, he hallucinates a large wave of blood rushing from the cell door, similar to a scene in The Shining

References to gangster films are also present. The boss of the Axe Gang, Brother Sum (琛哥) is named after Hon Sam (韓琛), the triad boss in Infernal Affairs.

The Harpists imitate The Blues Brothers, wearing similar hats and sunglasses at all times. When they are flattered by the Axe Gang advisor, one of them answers "Strictly speaking we're just musicians", similar to a line by Elwood Blues.

When Donut dies, he says "in great power lies great responsibility", a clear reference to Spider-Man, said by Uncle Ben before his death.

Afterwards, with his dying breath, he gets up, grabs the Landlord by the shirt and utters in English, "What are you prepared to do?", a nod to Sean Connery's character Jim Malone in Brian De Palma's 1987 film The Untouchables.

The final fight between Sing (who has been reborn into "the one" paying homage to Bruce Lee by wearing his costume in Enter the Dragon and using his fighting style)

the hundreds of gangsters imitates the fight between Neo and hundreds of Agent Smiths in The Matrix Reloaded.

The scene in which the Beast prompts an axe member to punch him harder is reminiscent of a similar scene in Raging Bull, with Robert De Niro's character prompting Joe Pesci's character.

The scene where the landlady confronts Brother Sum in the back of his car is a homage to Bruce Lee in Way of the Dragon, where he cracks his knuckles and gives a fast upper nod to the bad guy, telling him to back off.