Fridge Brilliance: In reality the girls admitted that the photographs were fake (though Frances maintained that the fairy bath was genuine) but not that the fairies themselves were. The Brilliance comes in with the fact that the girls are never seen taking the photographs in the films. A reporter also finds cardboard cut-outs of fairies in Joseph's room.
Hilarious in Hindsight: At Frances's first day of school one of the children asks "if you're from Africa, why do you sound so English?". This is quite close to a famous quote from the movie Mean Girls where a new student from Africa is asked "so if you're from Africa, why are you white?".
The film has Elsie inspired to photograph the fairies because she hears a soldier say he saw angels at the Battle of Mons. However, the Angels of Mons were based on a fake newspaper article (though presented as factual) which then bloomed into people saying they had actually seen them later.
Purely Aesthetic Era: The film tries to keep a consistently realistic Victorian setting, but as Arthur develops the initial photographs and calls to Elsie that they did come out, she throws up her arms and lets out a "YES!" in a thoroughly modern way.