The pack is transparent light blue in color with capitalized red writing that reads the product's name and a crown on top of said writing.
Role in episode
SpongeBob and Patrick are pretending to be astronauts with some water helmets while eating these marshmallows. SpongeBob then offers some to Squidward, but the latter turns down the offer on grounds that he doesn't eat junk food. However, due to him being annoyed by their astronaut roleplay, Squidward then agrees to have one and tries to roast many marshmallows, but keeps getting spit "molten foodstuffs" at him by Patrick.
Later, when Squidward is playing his clarinet, SpongeBob shoots a marshmallow through the clarinet into his throat to prevent the music from attracting a sea bear, force-feeding it to him in the process.
SpongeBob and Patrick believe them to be eaten by the astronauts.
Squidward considers this snack as junk food and indirectly says that Swedish Barnacle Balls are more appropriate to eat than Marsh King marshmallows.
The name might be a parody of the fast food restaurant Burger King.