Wayne once worked as a black operations agent until the shooting-related 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, who wanted to befriend him. Wayne kept to himself at first, but that changed 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, to which Homer allows him to stay in his house. After much talk, Wayne starts to open up 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' droppings on the lawn; he asks Homer about Wayne and ends 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, but not before bumping fists with Homer. However, Marge suggests a job where "a sadistic man with government experience can feel right at home": the DMV, where Wayne remembered a time when he was imprisoned in North Korea, and was also forced to write a play about North Korean leader, Kim Jong-il.
He later appeared in The Simpsons: Tapped Out as a character during the Secret Agent 2017 Event.
Wayne Slater is one of the few characters to actually show a remarkable physicality and fitness, as well as top-level martial artistic skills, marksmanship skills and espionage skills. He is also extremely resourceful as he created his own unique flame-t shirt gun to fight the Ukrainian mobsters.
He seems to have an almost sociopathic personality and rarely smiles, but he does show compassion with the Simpson family, whom he considers his friends, even teaching Bart and Lisa self-defense techniques.
Also, he seems to suffer PTSD (Post Traumatic Stress Disorder) regarding traumatic experiences of his past missions, which it's triggered by any thing or action in relation with his past memories and it causes him to panic and attack any person near him who triggered it and even had nightmares about his past traumas while staying with the Simpsons.
- Wayne shares some similities to Frank Grimes:
- Both of them were employees of Springfield Nuclear Power Plant.
- Both of them had a tragic past, as Frank Grimes faced hardships due to being abandoned by his parents at a young age, while Wayne had traumatic experiences from his years as a CIA agent.
- Both of them were almost awarded by Mr. Burns, but ended up losing their award, as Grimes loses the position of Vice President of the Plant due to Burns forgetting about him and giving it to a dog, while Wayne lost his because of him inadvertly attacking Mr. Burns.
- Both of them saved Homer's life, though Grimes was scolded by Mr. Burns as he spilled his acid and gave him a salary cut while Wayne was almost awarded for it.
- Both of them were invited to dinner at the Simpsons house, although Grimes refused to dine with them while Wayne did accept.
- Both of them were polite to the Simpson kids.
- Both of them dislike Homer when he tried to befriend them, though Wayne eventually warmed up to him, unlike Grimes who died hating Homer.