Nawazuddin Siddiqui's character is called Tehmur and walks with a limp, a reference to Timur the Lame (also known as Tamerlane and Tamburlaine), a prominent Mongol conqueror of the late 14th Century and an ancestor to the Mughal Dynasty who would rule India from the 16th to the 18th century.
The idea for the film came from an unexplained event witnessed by co-writer Zoya Akhtar and a group of her friends as they were driving down a deserted road one night and which haunts them to this day.
Aamir Khan and director Reema Kagti decided on having a mustache to give his policeman character a darker feel. However Khan grew it so long that it was against police regulations and it was only after being informed about this from a real police officer, that he let the hair and make-up crew trim it.
The script's original title was too revealing, so a new one was needed for the film. The three producers and two writers had trouble settling on a title they could all agree on. Thus plenty of titles were in consideration before Talaash was chosen.
Though set almost entirely in Mumbai, and extensively shot there on location, several key scenes were actually filmed in Puducherry, over 1000km away on the other side of India, and one underwater scene was shot at London's Pinewood Studios.