2 BIC Pens (you know the 100 pack ones you can get at the drug store)
a victim or two or three or four
Step 1: Open the pen
At this point you have:
a pen filler
a pen cap
a hollow pen with one plug in an end of it
Step 2: The second pen...
Step 3: Assembly
You can keep the actual pens for use as refills in other pens or deconstruct these after the joke and use them normally.