Return of Jolly Roger, the reformed villain from the first episode.
CASTLE THUNDER: Heard during the storm.
This is the second appearance of Jolly Rogers and his Pi-Rats since the series' second ever episode, "Piratsy Under the Seas (1989)".
The episode quasi-references episodes of two other Disney Afternoon franchises, both incidentally co-written by Mark Zaslove: The treasure cave on the island is located inside an ancient crocodile head sculpture atop a mountain, reminiscent of Gusto Gummi's dragon sculpture on the Deserted Island in "My Gummi Lies Over the Ocean (1986)".
In the very last bit of dialog, Chip mentions "gold fever", reminiscent of the condition that Scrooge McDuck suffers from in "Treasure of the Golden Suns: Too Much of a Gold Thing (1987)".