Barney's Magical Musical Adventure/The Little Mermaid

Barney as King Triton

Baby Bop as Ariel

The King as Grimbsy

Twynkle the Elf as Ursula (I know Twynkle the Elf is good,Ursula is evil)

Min and Tina as Ariel's Sisters

Michael as Prince Eric

Derek as Flounder