"The Wrath of Ruthless Ruth" (Season 1, Episode 13) is a "bottle episode" of Rapunzel's Tangled Adventure (originally Tangled: The Series ) that centers on a haunting at The Snuggly Duckling. The episode is widely considered a "solid piece" of storytelling because it balances supernatural comedy with a touching resolution about following one's hidden dreams.
Watch the full episode of 'The Wrath of Ruthless Ruth' to see Rapunzel help the Pub Thugs solve the mystery of the singing ghost: [S1E13] The Wrath of Ruthless Ruth