|Appearance||Day of the Dead|
Bub was apparently in one branch of the United States Military before the Zombie outbreak, possibly the US Army or Marine Infantry seeing as he remembers how to use a handgun later in the film. When the undead apocalypse occurred, Bub died and reanimated. He was one of the zombie specimens captured by the Seminole Storage Facility from the zombie-infested caves.
Rather than dissect Bub like the other zombie specimens, Logan instead tries to and successfully domesticates Bub. He demonstrates this to Sarah and Rhodes by giving Bub several objects which the latter recognizes from when he was alive, and remembers how to use. Bub is also able to speak (albeit with some difficulty) by repeating what Logan says, and more importantly is able to interact with living humans without seeing them as food.
Eventually, Logan rewards Bub by feeding him the fresh remains of Miller and Johnson. Later, Bub is able to figure out how to remove his chain and discovers Logan dead in the freezer where he eagerly shows the man that he removed the chain only to realize he has been killed. Enraged at his mentor's death, Bub takes a discarded gun and goes on a rampage in the complex, attacking Steel and shooting Rhodes.
Bub chases Rhodes through the complex, shooting him several times, until Rhodes runs into a horde of zombies. Bub gives Rhodes a mocking salute as the latter is dismembered and eaten alive by the zombie hordes.
Initially, Bub had the typical mentality of any other rabid zombie. However thanks to Logan's training and reeducation; Bub has regained some human intelligence. Logan concluded that Bub was able to unlock his memories from before his death and transformation into a zombie; as seen when Bub remembered how to use a razor to shave his face despite Logan never showing razors to Bub before. His intelligence continued to develop; allowing him to operate and use a pistol, escape his chains by loosening an exposed screw, and accurately concluding that Rhodes was responsible for Logan's murder. Despite his gradual humanization; Bub still craved human flesh, was unable to talk, and had some mental handicaps.
Bub's relationship with Logan improved to the point where he identified him as a friend instead as food; making no attempt to attack Logan and trusting him with anything. Bub was still hostile to other humans however, and attempted to shoot Rhodes with an empty pistol. After discovering that Rhodes murdered Logan; Bub was distraught, crying and sought revenge against Rhodes. As Bub watched other zombies devour Rhodes, he taunted the captain with a military salute instead of joining the other zombies in their feast.
- Bub is the third zombie in the series seen carrying a gun; The first was the zombie who took Roger DiMarco's assault rifle, and the second was the undead Stephen Andrews.
- Bub is also the first zombie in the series seen aiming and firing a gun.
- Much like Big Daddy, Bub is never seen attacking a living human for food, and thus only kills the main human antagonist as an act of revenge. Bub did, however, consume the butcherd flesh and organs of the recently deceased Pvt. Johnson and Pvt. Miller given to him by Dr. Logan, implying he has not entirely lost his taste for human flesh.
- Dr. Logan stated that he named Bub after the former's father.