Fantastic Beasts: 28 Easter Eggs & References You Must See

Back in the Harry Potter movies, when Harry visits the Ministry for the first time, he discovers that the Ministry uses enchanted interdepartmental memos in the form of paper planes. In America, the MACUSA use their own Stateside equivalent - enchanted paper mice.

Presumably the fact that the mice fight and shred each other when they come into contact is why the Ministry in England used to use owls (before upgrading to paper planes to avoid the droppings mess).