In the ending of the Sleeping Dogs DLC, "Nightmare in North Point", Not Ping Spoiler:agrees to finish her date with Wei Shen. As they walk away from the cemetery, she looks at the player with flashing light blue eyes and the laughter of the antagonist, Smiley Cat, is heard. This is a nod to Michael Jackson's "Thriller", in which Michael takes his girlfriend home and then looks at the audience with his werewolf eyes along with the laughter of the song's scary narrator being heard in the background.

There are a number of unlockable costumes that reference various gangster and martial arts films. These include:
• The Bon Gak - Ong-Bak
• Manhattan Melee - Rumble in the Bronx
• Hog Pen Row - Kung Fu Hustle
• Shen Zen - Fist of Fury
• Hai Tien Vintage Jumpsuit - Game of Death
• Part Time Assassin - Fulltime Killer
• Mr. Black - Reservoir Dogs

According to the official website, there were originally plans for a character named Fifi Mao. She was supposed to be a famous aging actress with connection to the Triad, but was ultimately cut from the game.

Concept art on the official Sleeping Dogs website reveals Thomas Pendrew's original first name to be Leonard.

Sleeping Dogs began development as a new IP under the title 'Black Lotus', even before Activision announced it as a True Crime title.

Sleeping Dogs was originally going to be published by Activision, under the title True Crime: Hong Kong. Square Enix purchased the rights to publish the game, but couldn't get the rights to the True Crime franchise, so the name was changed.

One of the radio commercials advertises a vacation to Panau, the setting of Just Cause 2, another game by Square Enix. It also mentions several landmarks that were key locations in Just Cause 2.