The Australian extras in the County Fair scene were told at one point to make some sounds for the microphones to pick up, to sound like real Fair-goers. After one take with their normal accents, they were reminded to be American. Most promptly started just repeating, "Oh my God" and some other modern-day Americanisms.
Most of the shooting was done in Victoria, Australia. As it wasn't the correct season in Melbourne during the county fair scenes, the trees surrounding the location were spray painted with non-toxic orange and yellow paint to make it seem as though it was autumn. And, rather than have extras getting motion sickness on the rides, the art department sculpted bodies out of polystyrene and took casts of their own faces that were put onto the dummies. These dummies were painted and dressed up and strapped into rides; going round and around for about a week - and no motion sickness. Each of their faces (about 5 of them) were on all of the 60 or so dummies.
The spider introduces herself as "Charlotte A. Cavatica," which refers to the barn spider's scientific name, Araneus cavaticus. The old scientific name was feminine - Aranea cavatica.
There were 47 Wilburs on set because the piglets grew up so fast. Also, each one was taught only one "trick", like to stare up or to walk a certain distance.
The names of the two crows, Elwyn and Brooks, is a reference to author E.B. White, whose full name was Elwyn Brooks White.