The idea of this joke is momentum.
You are basically going to glue the cup to some string and then attach it to the items in the cup.
The key to this is that when people grab the pin, marker or whiteout, they are going to believe it is free from the cup and then they will be pulling it away with enough force to scare them when the cup is soon to follow.
Step 1: Supplies
5) needle nose pliers
Step 2: Attaching the String to the Pins and Markers
you can either melt a hole trough your writing utincel
You can tie the string around it and glue it with Gorilla Glue.
You can tie the string around the inner pieces and have the string come out of where the pin writing device is usually.
Or just tying onto the pin by various ways
Allow enough string for the pins to reach the top of the cup.
Tip* cleaning the surface is always a great idea.
Put enough to allow for some good bonding.
If you put too much you will be holding the pins for a long time waiting for the glue to dry.