Wayne once worked as a black operations agent until the shooting death of the wife of a Ukrainian mobster boss. He fled to America and got a job as a security guard at the Springfield Nuclear Power Plant, where he met Homer. Wayne kept to himself at first, but that changes when he stopped Snake Jailbird from robbing Moe's Tavern. The news crew meets up with him at work, where he is being rewarded for his heroism. Troubles from the past cost him his job when he attacks Mr. Burns after having a painful flashback as he is being awarded. After much talk, Wayne starts to open about his past, and admits to the Mafia being on his case. Later, the widowed mobster finds the video of Wayne attacking Mr. Burns and goes to Springfield.
When the mobster arrives he finds Homer washing the dogs leavings on the lawn; he asks Homer about Wayne and end up kidnapping Homer when they find out that Homer is Wayne's friend. When Homer gets kidnapped by the Ukrainian mob, Wayne knows he's the only one who can save him. Wayne tracks the group down in an ice hockey arena thanks to the GPS system Homer swallowed (since they were left out in a bowl). Wayne finds Homer trapped underneath the ice in the arena. After confronting the mob and taking out all the mobsters, Wayne freed Homer. Wayne decides to leave Springfield, claiming he can't stay in one place. However, Marge suggests a job where "a sadistic man with government experience can feel right at home": the DMV.
Wayne Slater is one of the few characters to actually show a remarkable physicality & fitness, as well has top-level martial artistic skills, marksmanship skills & espionage skills. He is also extremely resourceful as he created his own unique flame-t shirt gun to fight the Ukrainian mobsters.
He also seems to have an almost sociopathic personality, but he does show compassion with the Simpsons family, whom he considers his friends.