You stare at the lighter, the fork, and the rope. The lighter is an ordinary plastic lighter (which contains lighter fluid, a colorless oil which is, obviously, flammable). The fork is made of some kind of metal (you're not sure which, but it's not sterling silver), and has four tines (the pointy bits). The rope is about as thick as your finger, is made of something organic, and is just long enough to stretch from the floor to the ceiling.
You then start thinking:
"What would MacGyver do?"
Well for starters, he'd sweep that sweet mullet back and get to work!
Then he would build a flamethrower to melt through the walls, of course! He has everything he would ever need!
Just don't burn your mullet!
And certainly do not, on any account, burn the rope!
For it is where your power truly lies....
Time is running out, and you need to act fast before the marshmallow explodes. The fate of the free world rests on your shoulders...
Do you know what else rests on your shoulders? That's right! Your sweet sweet mullet.
Do you:
Toss the lighter into the marshmallow wall
Place the rope in the wall like a wick and light it on fire?
Tie the rope to the fork, stick it to the ceiling, climb up and burn a hole to escape?