Add 1/2 cup of the butter into a pot and then add 1 kernel of popcorn. Turn the stove to medium heat until that one kernel pops, and then turn to medium-high heat.
Add the rest of the kernels and keep the heat on medium. Make sure to put the lid on top! It will take a few moments for the kernels to start popping.
As soon as they start popping rapidly, shake the pan side to side so that the kernels move about that aren't popped so can pop.
Once the popping slows, turn off the heat and shake.
Line a baking sheet with parchment paper and pour the popcorn on the baking sheet. Spread out.
Melt the blue melting chocolate chips in the microwave based on the bag directions.
Pour the melted chocolate into a plastic bag and snip off the corner.
Drizzle the blue chocolate over the top of the popcorn and add the mermaid sprinkles.
Put the pan in the fridge or freeze it for 10 minutes to harden.