The pack is transparent light blue, with capitalized red writing reading "Marsh King" and a crown on top of the writing.
Role in Episode
SpongeBob and Patrick were pretending to be astronauts with some water helmets while eating the marshmallows. Squidward was trying to roast some marshmallows, but Patrick kept spitting (as Squidward said) "molten foodstuffs" at him. Later, when Squidward was playing his clarinet, SpongeBob shot a marshmallow through the clarinet into Squidward's throat.
SpongeBob and Patrick believe it 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's marshmallows.