- Cross-Dressing Voice: While it is averted in the English version where Ben is voiced by David Rowle, it is played straight in the Japanese version where Manami Motoue voices him.
- Multiple Languages, Same Voice Actor: Brendan Gleeson (Conor and Mac Lir) and Fionnula Flanagan (Granny and Macha) voiced their respective characters in English and Irish.
- What Could Have Been:
- Word of God said that they were considering putting in the footage from the conceptual trailer into the film, but the film and story evolved to a point where they couldn't put in the conceptual trailer within the film regardless of how much they loved the concept trailer.
- Tomm Moore toyed with the idea that Song of the Sea could be a comic that he could do alone or with a little team, but figured that the story was about music at its heart and knew it had to be an animated movie.
- Early concept art and the conceptual trailer suggest that Ben was originally going to be way younger than he is in the final film.
- Early drafts had Saoirse leaving with her mother in the end, but this was deemed too sad.
- Moore mentions there would have been a bit more specification of Mac Lir's grief and who exactly he lost but it was dropped to keep the theme and plot simplified.
- The scene where Ben scares Saoirse with the story of Macha had to be toned down so Ben didn't come off as too mean.
- Concept art shows that filmmakers toyed with the idea of having leprechauns in the film, something that ultimately scrapped.
- Like the scene with Ben scaring Saoirse above, the scene where Granny takes the kids to the city had to be changed. Storyboards show her as more cold and impatient, but the final film has her more guilty about it.
- Saoirse was originally going to be four years old, but she was later aged up to six.
- Early concept art shows that the film was going to center more around Saoirse, Bronagh and the seals.
- Write What You Know: According to the commentary, director Tomm Moore states that the film is based of several aspects from his childhood. The film is set in October of 1987, which Moore remembered as rainy, and windy. Some characters also relate to Moore's family and pets from memories, pictures, etc.
Trivia / Song of the Sea