Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: The film opens with Tammy at cheerleader practice, while her boyfriend Michael walks in from football practice to observe. The two of them meet Byron, Tammy's gay friend, who approves of Michael as her new boyfriend. Shortly thereafter, Tammy's violent and jealous ex-boyfriend Billy arrives with his gang and harasses Michael. A fight erupts between the two. However, the police arrive to break up the fight and take Billy into custody, but Tammy, unable to deal with the events, breaks down and runs away in tears.
The scene then cuts to a figure of a T-Rex in a dark warehouse as two people, Dr. Wachenstein and his assistant Helga, walk through the doors. The lights come on and the T-Rex figure begins to move, being controlled by someone in a room. The Dr. is impressed by the robotic dinosaur's strength, and reveals his plan to implant a living human brain into the robot to give it consciousness, mobility and, "immortality".
Later that night, Michael sneaks out to see Tammy. They are soon interrupted by Billy and his thugs, who chase and catch Michael. They throw him into the wild Animal Park where lions and jaguars run loose. A lion mauls Michael and he is left in a comatose state. He is brought to a hospital where his intoxicated uncle watches over him.
Whose ex-boyfriend shows up to harass Michael?