David Madison is the main protagonist of the 1980 horror film Alligator. He was a police detective with homicide in the beginning, being fired later and killing Ramone, the giant alligator menacing his town, independantly.
Little is known about David's past, other than he wanted to be a cop as a kid, studying history and psychology in a college, before becoming a cop, and later a homicide detective. Eventually, he was given a case at a hotel, where his partner, Jerry, ended up shot with David's gun after he was bluffed from behind. This event left him and his reputation scarred, with David becoming a believed unlucky partner for anyone from then on.
Madison made his debut in the film, picking up a puppy at a pet store as a home pet, before being called into work. At the scene, he saw that a dismembered arm had been found, which he put in a plastic wrap. Madison's boss, Chief Clark, then arrived and called him outside, where a woman identified a rare dog species specimen as her pet, but was too large. Investigating both cases, Madison is informed that a dismembered leg was found, which he identified as another victim than the first. Visiting Slade Pharmaceudical, a local company known for testing animals, which had their animals silenced, like the dead dog found. The next day, Madison had to attend a press conference about the two victims, which he hated due to the reporters. There, Thomas Kemp, a reporter who Madison especially disliked, revealed his past, where he lost a partner during a hotel mishap. In response to the two dead people killed, Madison decided to search the sewers, taking along the only person willing to partner with him, Officer Kelly. Though they got along well, Madison was pranked by Kelly once, before they encountered Ramone which, despite Madison's attempt to help, dragged away and devoured Kelly when a manhole doesn't open. Waking up in a hospital, Madison forcibly left with Chief Clark after Kemp appeared. Madison and Clark went to herpetologist and author Marisa Kendall, who said that an alligator could not survive in the sewers. Leaving with her book to make strategies, Madison went on to lead an operation to kill Ramone after Kemp provided proof of its existence at the cost of his life. However, Ramone avoided the national guardsmen and policemen.
Later, Madison was lectured by Clark after Ramone broke out of the sewers and began to terrorize the town. The next day, Madison was, along with Kendall, amazed at Ramone's size when they discover it by tracks at the river bank. He was soon relieved of his operation by Colonel Brock, a big-game hunter and tracker hired to kill Ramone, who he immediately disliked due to their conflicting personalities. Requesting help from Kendall and promising to buy an iguana in return, Madison narrowed down the origin of Ramone's size to Slade Pharmaceudical, but was later fired when he tried to inform Chief Clark of this, as Slade himself had called the mayor to do so. After stealing necessary equipment to build a bomb from the evidence room, Madison informed Kendall of his intension, who joined him to help out. They found Ramone's nest in the sewer, before going to Madison's apartment, where they began an intimate relationship by having sex, before going out to supper. At a cafe, they were informed of Brock's death by Ramone after hunting after dark for him, and Madison hurt Kendall's feelings. Later, he had a nightmare about Kelly, before going to Kendall's house to see her and meeting her rather talkative mother, Madeline. Kendall forgave Madison, and they ventured off to kill Ramone, which headed for Slade mansion after evading police boats. Madison and Kendall arrive at the gate, where he forced the doorman to let them in at gunpoint. Chasing Ramone, they realize he headed back into the sewers. Knowing his destination, Madison going into the sewer with his bomb, and instructing Kendall to ensure the intended manhole was clear for escape. He found and shot Ramone, luring it to where he wanted and rigging the bomb to explode, only to be hit by its tail. When he tried to escape, a car drove onto the cover of the hole.
However, Kendall arrived in time to move the car, and Madison just barely got out in time to evade the explosion of the bomb, which blasted Ramone to pieces. Later, Chief Clark arrived, and Madison jokingly said that he would put him up with Kendall's mother, before they stood over the manhole and commented on their success.
David Madison is a very serious and, normally, nice man, but has a touchy sense to him, which will cause him to hurt others' feelings some times. After he met Marisa Kendall, though they didn't immediately click, they fell in love. Madison also has a sense of humor, as he jokingly remarked that he would lock his former boss, Chief Clark up with Kendall's talkative mother at the end of the film after the latter claimed to have never doubted him. Though reporter Thomas Kemp and Madison had a very antagonistic relationship, after Kemp was killed providing evidence of Ramone's existence, he talked with some respect for his memory, despite claiming all the latter wanted was to make the front page of the local paper. However, Madison and Colonel Brock, the professional big-game hunter and tracker hired by the mayor to kill Ramone, had a more hostile relationship, and Madison had no respect for his memory at all, claiming when he died that it was his fault in a rather distasteful tone.
Madison was very skilled at doing his job, despite being considered bad luck due to the accident in the past where a partner was killed. He was an excellent shot, and quite knowledgeable about various weapons, knowing how to build and use a bomb, which he used to kill Ramone in the film.