The pirate queen looks exactly like Sandy Cheeks, except wears a dark green dress, dark gray coat, a dark gray pirate hat with a gold earring on it, dark gray boots, a red headband on her head, and a left eyepatch.
Role in episode
She invaded Mr. Krabs' cargo ship with her crew but was eventually stopped by him and then taken to the brig. However, Mr. Krabs gave her a pie with a candy key inside it.
Inexplicably, she was able to breathe underwater despite lacking an air helmet. It's possible that pirate queen wasn't actually a squirrel, as well as other characters in Mr. Krabs' story possibly had fake appearances either.