Originally, Sebastian was to have an English accent. It was lyricist/producer Howard Ashman who suggested he speak with a Caribbean accent. This opened the door to calypso-style numbers like "Under the Sea," which won the Academy Award.
In the opening scene when King Triton arrives at the arena, Mickey Mouse, Goofy, Donald Duck and Kermit the Frog can be briefly seen in the crowd of sea-people as mermen when he passes over them.
Ben Wright's final film, released four months after his death following heart surgery. When he got the part of Grimsby, Prince Eric's manservant, the younger Disney folks had no idea that he had been the voices of Roger in One Hundred and One Dalmatians (1961) and Rama in The Jungle Book (1967). He had to tell them.
Ariel's rendition of "Part of Your World" set a precedent for subsequent Disney animated musicals where the protagonist would vocalize his or her desires early in the film. The song was referred to by Howard Ashman as the "I Want" song. See also "Belle" in Beauty and the Beast (1991), "One Jump Ahead" in Aladdin (1992), "I Just Can't Wait To Be King" in The Lion King (1994), "Just Around the Riverbend" in Pocahontas (1995), "Out There" in The Hunchback of Notre Dame (1996), "Go The Distance" in Hercules (1997), "Reflection" in Mulan (1998), "Strangers Like Me" in Tarzan (1999), "Perfect World" in The Emperor's New Groove (2000), "I'm Still Here" in Treasure Planet (2002), "Almost There" in The Princess and the Frog (2009), "When Will My Life Begin?" in Tangled (2010), "For the First Time in Forever" in Frozen (2013) and "How Far I'll Go" in Moana (2016).
This is the movie (along with 1986's "The Great Mouse Detective" - also directed by John Musker & Ron Clements - and 1988's "Oliver & Company" - whose opening song "One Upon a Time in New York City" was written by Howard Ashman - and the 1985 debut of Walt Disney Pictures Television Animation & its very first program "Adventures of the Gummi Bears") that brought Disney into its renaissance era in 1989, after repeated defeats at the box office.