The song young Ursula sings in the bar is Fathoms Below, the opening song from The Little Mermaid (1989).
The song Ursula sings as a mermaid to lure ships is actually the song that Ariel sings when Ursula took her voice in The Little Mermaid (1989).
The title of this episode is a reference to Ursula's song of the same title in The Little Mermaid (1989).
This episode explains how Ursula and Captain Hook have met in the past.