The Mindless Repulsive Pharmacists are the main antagonists of the Phineas & Ferb Halloween special Night of the Living Pharmacists.
They were accidentally created by Heinz Doofenshmirtz when he shot his brother Roger Doofenshmirtz (the
Mayor of Danville) with his Repulse-Inator during the unveiling of Danville's first water tower. However, since the -inator was to require a lot more power than usual (evident by a number of extension cords attached to the machine), a power surge strikes the -inator as it fired at Roger, turning him into a zombie version of Heinz, much to everyone's horror, including Heinz, who is now extremely furious of the fact that he's being used as a literal meaning of repulsiveness. This results an epidemic in which anyone who came in contact with a Doof zombie becomes one. The virus managed to spread all throughout the Tri-State Area, even infecting almost all of the O.W.C.A. animal agents. (However it has more of a werewolf affect on them). Doofenshmirtz is the only one who is immune to their touch (Probably because they all look like him).
While keeping himself and his friends away from being infected by using rubber to insulate from the infection, Phineas soon learns that the contagion is only caused by static electricity and the Fireside Girls deduct that the source is somewhere in Doofenshmirtz Evil. Inc. In the meantime, Doofenshmirtz initially attempts to take advantage of the situation to take over the Tri-State Area, but realizes that his zombie counterparts have gone out of control, and aids Perry from getting infected. Eventually, after arriving back at his lair via helicopter, Doofenshmirtz finally spots the kids arriving, including his own daughter Vanessa. After Doofenshmirtz explains about the events that caused the contagion, Phineas and the gang decide to come up with a plan: to use the water tower to douse everyone in water to turn them back to normal (since water can neutralize static). Using spare parts from Doofenshmirtz's lair, Doofenshmirtz and the kids build a pulley system and a giant sprinkler. However, more Doof zombies arrive, and Phineas, Ferb, and Isabella head up to the tower while Doofenshmirtz, Candace, and Vanessa deal with the zombies. Eventually, Perry and Vanessa get infected, much to the anger of Doofenshmirtz, who then offers himself as bait (despite being immune to the zombies) to buy the kids some time.
After reaching the water tower, Phineas and Ferb get infected, but before Isabella becomes infected, she manages to turn on the sprinkler, causing all the water from the tower to spread around all of Danville, turning everyone back to normal. As a relieved Doofenshmirtz assures that he won't be bringing a zombie apocalypse again, Phineas and Ferb comment that everyone in Danville is finally cured, but Isabella comments that the rest of the world is still infected, as there are still many other Doof zombies surrounding the walled city of Danville. It is unknown what happens next afterwards, although it is implied that the entire episode was just a horror movie that Stacy was watching.