The yellow King K. Rool represents King Knight, a king-themed knight who wears golden armor.
The stage represents the interior of Pridemoor Keep, a fortified castle stage which serves as the location of King Knight's boss battle.
The music track represents the musical theme of the Mega Man series, which serves as the inspiration of Shovel Knight.
King K. Rool starting off with a Star Rod and frequent dash attacks reference King Knight's usage of his staff and a midair body slam to attack.
Other trivia:
This spirit's Weight ↑ ability references King Knight's golden armor, which makes him a heavyweight character.
