She goes into the castle to save Princess Pearl by telling the guards that she was going to torture SpongeBob, Patrick, and Squidly but just went up to save Princess Pearl. When the jellyfish dragon comes up The Dark Knight gets zapped by it and SpongeBob and Patrick save Pearl from poured into the lava.
The Dark Knight is a brown color, and she is very tall but she is revealed to be very small when she is defeated. She wears orange and yellow medieval armor. The Dark Knight also carries around a weapon known as a flail. It is revealed when she is defeated that she then had a passion for karate, and that she loves it more since SpongeBob and Patrick went back to present time.
- Unlike Sandy, she is not wearing an air helmet which does not make sense at all because the Dark Knight is a land creature. It's possibly due to Planktonamor's magic that keeps her alive undersea.
- Sandy possibly inherited her passion for karate from the Dark Knight, seeings how the Dark Knight learned karate and that it was possible that she passed it down to her descendents including Sandy.
- The name, Dark Knight, may be a reference to Batman: The Dark Knight, or the older dark knight from Scooby Doo: Where Are You? first episode What a Night for a Knight.
- When the Dark Knight battled SpongeBob, she didn't use her morning star/flail for some reason.
- (male voice) HALT! Who goes there? (to SpongeBob, Squidly, and Patrick)
- (male voice) I ask once more. Before I rip you limb from limb, reveal thyself!
- (female voice) Rrrrrrrriippppp!