Skeletor's former name is revealed to be Keldor. This name was first mentioned in one of the last mini-comics produced by Mattel and published with Masters of the Universe action figures, titled "The Search for Keldor". In this story, Keldor is said to be King Randor's long lost brother, and a connection between Keldor and Skeletor is strongly hinted at. In the Mike Young series, there is never any mention of Keldor being related to Randor, but a biography on the DVD release did reveal them to be half-brothers.
Merman retrieves the Coridite Crystal from the Sea of Rakash. In the Filmation series, Coridite was a powerful mineral mined by the tiny Widgets, from which He-Man's harness was forged. The Sea of Rakash had previously been used as a location in both the Ladybird series of books and in Marvel's Star comics series.