Chance

Chance is a twentysomething slacker living in Los Angeles, who relies on a trust fund for finances. Her friend Simon, a not very successful telemarketer who is self-conscious about his body odor, has been sleeping on her couch. One day, Simon comes home from the grocery store to find a woman in Chance's bed who won't wake up.
The film then goes back several months. Chance is annoyed when Rory, a struggling actor with whom Chance had a one-night stand, appears at her door and becomes emotional trying to convince her that they have a connection beyond just sex because they really talked afterward. Chance and Simon spin a story about meeting in a mental institution, which makes Rory uncomfortable enough to stop crying and to leave.
Simon tricks Chance into answering a phone call from her mother by telling her that it's a man named Jack whom she was immediately attracted to when she met at a nightclub. Her mother, Desiree, is calling to tell her that she is coming to visit. Trying to escape spending time with her mother, Chance persuades Simon to switch roles with her for the weekend and Simon spends time with Desiree pretending to be Chance until Desiree tells Simon that she needs to talk to Chance about something in particular. Desiree tells Chance that she is divorcing Chance's father, Malcolm, because he is in a relationship with another woman named Heidi.
Upset, Chance tells Simon about her parents' divorce and reveals that Desiree wants to stay with them for a while. Chance is suspicious when Simon tries to offer some comfort, and he begs again for $200 to pay off some unpaid parking tickets. Though hesitant to loan anyone money because of a bad experience with her first serious boyfriend, Chance agrees to give him the money for playing along with her charade for her mother.
Uncomfortable with the idea of her mother living with her, Chance arranges for Desiree and her to have dinner with Malcolm and Heidi. Chance also invites Rory and, as Chance had hoped, Heidi is immediately smitten with him because she watches the soap opera in which he stars. When Rory manages to get Heidi out of the room, Chance asks her parents about the divorce. Malcolm reveals that Desiree had suggested that they experiment sexually with Heidi, and Desiree felt rejected when Heidi preferred him. Desiree insists that he seduced her, but Malcolm denies it. Malcolm says that while attractions may come and go he loves her.
Chance goes out to a club one night and meets a woman named Sara, who makes sexual advances on her. Chance brings Sara home with her, and after spending a day in bed together, Sara suggests that they take some drugs. Chance refuses and takes the drugs away. Chance leaves her apartment the next morning, and when she returns she finds Simon in her bedroom with Sara, who has apparently overdosed. Chance initially tries to comfort Simon, but soon she herself begins to freak out when she realizes that she has a dead woman in her bed. Overcome with emotion, Simon kisses Chance and they have sex. Afterward, the two quickly begin to fight about the significance of the sex and Simon leaves the apartment.
The next morning Chance awakes to find Sara, alive, sitting at the kitchen table. Sara tells her that she wasn't dead, just "resting." She thanks Chance for the place to sleep and then leaves. Chance then realizes that Simon never came home.
Simon has run into Jack, who recognizes him from the nightclub. The two make small talk until Simon realizes that Jack is hitting on him. Simon begins laughing and at Jack's confusion tells him that Chance has a huge crush on him and thinks that he is straight. Simon then tells Jack about what had happened the night before and about his frustration and attraction to Chance. Jack tells Simon that, even though he is gay, he sometimes has sex with women because he needs the contact with human beings, and Simon realizes that he needs that human contact too. Simon returns to Chance's apartment, and Chance is happy to see him, greeting him with a hug. They apologize for their actions and both admit that they are ready to try a relationship.

Question: Who pretends to be Chance?
Answer: Simon