Delhi Belly

It revolves around three roommates, journalist Tashi (Imran Khan), photographer Nitin Beri (Kunaal Roy Kapur) and Arup (Vir Das) leading an unkempt and debt-ridden life in a shoddy apartment. Tashi's ditsy fiancee Sonia (Shenaz Treasurywala) is an air hostess who agrees to deliver a package for Vladimir Dragunsky (Kim Bodnia) to the Somayajulu (Vijay Raaz), without realizing its contents or that Somayajulu is a gangster. Sonia asks Tashi to deliver the package. Tashi, in turn, asks Nitin to do so. But Nitin is unable to do so as he is experiencing 'Delhi Belly'. Nitin hands Sonia's package to Arup for delivery to Somayajulu, along with a package containing his stool sample for delivery to Nitin's doctor. Arup mixes up the two packages which makes Somayajulu furious and he starts the investigation by interrogating Vladimir.Meanwhile, Nitin photographs his landlord with a prostitute. He sends an envelope with the photographs to his landlord to blackmail him. Tashi is with Sonia, when his colleague Menaka (Poorna Jagannathan) calls him on the pretext of work. When he reaches the place he realizes that it is just a party and Menaka called him just to have fun. Menaka's ex-husband Rajeev sees them together and gives Tashi a black-eye in a fit of jealousy. Tashi retaliates and knocks Rajeev out. As Tashi and Menaka leave they are chased by a furious Rajeev and his friends who shoot at them. The duo barely manages to escape.Vladimir informs Somayajulu that the mix-up must have been caused by Sonia as she didn't know what she was carrying in the package. Somayajulu calls Sonia, informs her about the mix-up and asks her to give him the address of the person who had delivered the package. When Tashi arrives into his apartment, he walks into Somayajulu who has Arup standing on a stool with a noose around his neck. On hard interrogation, Somayajulu discovers the mix-up and realizes that the package must be with Nitin's doctor.Nitin gets the package from his doctor's office, wherein Somayajulu finds his thirty diamonds hidden inside. Upon recovering his booty, he orders his henchmen to kill the three roommates. One of them is about to shoot Tashi, when another kicks the stool on which Arup was standing to hang him. Luckily for the roommates, the ceiling of the apartment caves in, since it can't take Arup's weight. The cave-in injures and knocks-out Somayajulu and his men. Tashi, Arup and Nitin escape along with the diamonds and spend the night at Menaka's place. The next day they sell the diamonds to a local jewellery store.As the roommates prepare to get out of town with the money, they a call from Somayajulu who has kidnapped Sonia. He threatens to kill her if they don't return the diamonds. The trio, try to buy back the diamonds from the jewellery store, who demands double the sale amount.Without the money, Tashi comes up with a plan. Nitin, Arup, Tashi and Maneka disguise themselves in burqa and go back to the jewellery store. They con the owner, gag him and forcefully take back their diamonds and return his money. They make their get-away in Tashi's car with the police on their tail and make their way to the hotel where Somayajulu is holding Sonia. As they are about to make the exchange with Somayajulu, the police arrive at the hotel room. There is a shoot-out between the police and Somayajulu's gang.Nitin, Arup, Tashi and Sonia, who had hit the floor during gunfight,are left as the only survivors. Menaka is upset to learn about Tashi's engagement and walks away from him. Tashi breaks off his engagement to Sonia. Later, it is revealed that Nitin did not return the cash to the jewelery store owner, and had kept the money for himself. The film ends when Menaka comes to the roommates' apartment to return Tashi's car's wheel cover lost while escaping from Rajeev. Tashi jumps into her car through the open window and kisses her.Producer-actor Aamir Khan is seen in a song and dance performance during the credits at the end of the film.

Question: What is in the package that was supposed to be delivered to Nitin's doctor?
Answer: Stool sample; Stool sample