They are very simple, just time consuming.
You can make the popcorn one of two ways.
1.) Just pipe on some buttercream with a round tip.
2.) Use mini marshmallows. Use a scissor to cut an X shape into the marshmallow. Pinch the opposite end a bit to open up the X shape. With a paintbrush, add some yellow food coloring to the center of the X to look like butter. (I did that part after putting the marshmallows on the cupcake.) Put a layer of buttercream on the cupcake, then stick the marshmallows to that.
To make the wrapper, you can either buy pre-made popcorn wrappers, or buy some nut cups at the craft store and color every other section with a red Crayola marker.