There was a swear jar on set. Whenever an actor cursed, they needed to put money in the jar. At the end of shooting, the total was given to charity. Allegedly, Colin Farrell was the worst offender and was responsible for the majority of the money.
The original model for Dumbo was somewhat photorealistic, but eventually scrapped for the more expressive one seen in the movie.
Extras in circus scenes were not actors, but actual circus acts. Over 600 circus performers from around the world were hired for crowd scenes.
Filmed entirely on a sound stage--not even the outdoor scenes were exterior shots.
Eva Green is afraid of heights. She was able to overcome her fear during filming, with the help of a professional performer who trained her in her stunts.