The Other Darrin: Dr. Schrader, Flora and Don Paolo, during their guest appearances at the beginning, have different voices from the games. It's understandable with Flora, since Lani Minella is a U.S.-based actress and the movie was dubbed in the United Kingdom, but it is somewhat puzzling why Don Paolo has a different actor, since Chris Miller voiced both Layton and Don Paolo.
Voice changes happened in the Italian dub too. Not only Don Paolo and Flora have different voices in the beginning scene (and is more puzzling than in English, since in Italian not only Layton and Don Paolo have the same voice actor, but the same also applies for Luke and Flora), but also Emmy and Grotsky have different voices than in the games (Tania De Domenico and Mario Zucca instead of Emanuela Pacotto and Stefano Albertini). Amusingly, is not the case for Descole: while the movie was released before The Last Specter, Lorenzo Scattorin was kept as his voice in the games too.