Human Nature is a 2001 comedy film, written by Charlie Kaufman and directed by Michel Gondry. It was Kaufman's second produced screenplay, following his debut with Being John Malkovich; the film stars Tim Robbins, Rhys Ifans, and Patricia Arquette.
Most of the movie is told as flashback: Puff testifies to Congress, Lila tells her story to the police, while a dead Nathan addresses an unseen audience in the netherworld.
One day Lila and Nathan go for a hike where they discover Puff (named by Gabrielle, Nathan's assistant, who says that he reminds her of a dog she had as a girl), who has been raised in the wild. Puff's father believed himself to be an ape and kidnaps his son from his human mother, despite years of therapy, to raise him in the wild. Nathan decides that he will train Puff as he has trained mice.
Gabrielle is Nathan's assistant who is determined to seduce him with her convincing French accent. She assists Nathan as he trains Puff to be a human zapping him with a shock collar as discipline. She calls him at home one day while Lila is in the bathroom. When he answers, Lila asks who it is. Nathan replies that it is someone from work, but she asks WHO it is from work. He walks into the bathroom, leaving the phone on the bed, and finds Lila covered in shaving cream shaving her entire body. Disgusted, he runs out leaving Lila terrified. Gabrielle hears the argument and takes advantage of the situation to head to the office in provocative lingerie and seduce Nathan. Only when Puff wittnesses Gabrielle and Nathan having sex right outside his glass cage does he show interest in learning the human ways.
Puff learns quickly from questionable techniques. Lila shaves even her hair and eyebrows and begins using a wig and pencil. Gabrielle makes Nathan choose between her and Lila, like in "Sophie's choice" only this was "Nathan's choice". When he offers a "but" she storms out on him. Lila offers to help a very uninterested Nathan. Despite Lila's desperate attempts at becoming more ladylike, Nathan continues to think about Gabrielle.
Once Puff has made significant improvement he is allowed to visit the city and is given the surprise of a comfy room rather than a plain white one complete with a painted chimney, as well as a key so that he may leave as he wishes. Puff uses his new-found freedom to visit strip clubs, prosititutes and watch dirty movies.
Nathan tells Lila that he will check up on Puff but instead goes to Gabrielle's apartment. An unattractive Gabrielle is talking on phone in a clear American accent when Nathan knocks at her messy apartment. She quickly fixes her apartment and changes into a lustful French woman. When Nathan returns home to Lila, she asks him what he did that night. He lies but she tells him that she had just picked up Puff from a night in the city. Nathan tells Lila that he is in love with someone else and she leaves him.
Puff continues to improve and appears in several events with Nathan and Gabrielle. Gabrielle is now trying to seduce Puff, however. When the three of them are in the lab, a dwarf walks in and forces Nathan and Gabrielle into the glass cage that was once Puff's room. A now hairless and buff Lila walks in and orders that they be tied up. She puts the shock collar around Puff's neck and takes him with her.
Lila takes Puff to the wild and tells him that she will retrain him into the free being that he once was. He protests but she shocks him. They have sex and continue to live happily as apes. Nathan can now not stop thinking of Lila and shows up in the wilderness. At first Lila and Puff grunt but begin speaking because Nathan is threatening them with a gun. However, Nathan drops the gun when he kneels to Lila and Puff picks it up. Nathan is shot in the head. Although one never sees who shot, both Puff and Lila testify that it was her, while Nathan reports that it was Puff. Lila tells Puff that she will return to civilization and confess to the murder but Puff must stay to be free. He agrees but only after testifying to Congress about human kind.
When Lila is in jail, Puff walks out to fulfill his promise to Lila and live free. Reporters and spectators follow as he strips his clothes. Right before he heads into the bush a woman stops him claiming to be his mother. He simply tells her that he is glad to meet her, but he is an ape, as his father was. Saddened she tells Puff that she's in the book in case he ever wants to drop her a line. Puff only replies that he is an ape, and apes don't drop lines. Puff heads off and the crowd that followed disperses. After a few seconds, a car drives up and Puff emerges from the bushes and into the car. Inside, Gabrielle, again with her French accent, greets him with a kiss and a jacket. As they drive off together Puff observes the wilderness and the tent where he lived with Lila. The mice, which Lila had released, appear on the side of the road, trying to hitch a ride to New York.
Though not as big a success as Gondry and Kaufman's next collaboration, Eternal Sunshine of the Spotless Mind, the film has garnered a large cult following of Michel Gondry and Charlie Kaufman fans alike.