Sore Ike! Anpanman: Yuurei Sen wo Yattsukero!!

The separated sisters Melonpanna and Rollpanna both befriend a mysterious horse Marin. She shows Rollpanna her treasure, a sunken ship she raises from the depths. Baikinman sees this and is inspired to build a ghost ship of his own with help from Dr. Hiyari. He also plots to turn Rollpanna fully evil in order to use her to defeat Anpanman.

(Source: Anime News Network)