Buttercup is dressed as Dutch vampire hunter Abraham Van Helsing from Irish author Bram Stoker's novel Dracula.
When Buttercup is removing the curse, she speaks in pig-Latin and sprinkles holy water in the Mayor. It's probably a spoof the 1973 film "The Exorcist", where the priest speaks Latin.
"icks-nay the ickles-pay. They make you azy-cray" or "Nicks / Nix (stop) the pickles. They make you crazy"
Then the dog's name from the anime Blue Exorcist: pa-dapa-pada-pa-pa
Then she says the lyrics from "Witch Doctor" a 1958 American novelty song: "Walla walla, bing bang"
The iron (small applicance) on the shirt is in reference to the belief that "iron" (the metal) drives out devils.