In the original script, Ray and Ken are British, but when Colin Farrell and Brendan Gleeson came on board, the characters were changed to Irish as to suit their natural sensibilities.
In order to create the feeling of the holiday season, Christmas decorations were kept in some streets of Bruges until the end of March. The town council made an official communication to the people of Bruges explaining the reason why.
Except for the flashback, Ray wears a single outfit throughout the whole movie. While he does remove his jacket and unbutton his shirt, he has no other change of clothes. Ken, on the other hand, has several wardrobe changes.
When Pieter Lanchals was executed in 1488, Maximillian of Austria's punishment was that Bruges keep swans forever.
When Ray refers to the dwarf in Time Bandits (1981), he is thinking of actor David Rappaport, who committed suicide in 1990.