Frank the Frog. He will keep you from losing your pen!
Instead of a string this design used an emotional attachment to keep you from misplacing your pen. Frank will be deeply sad if you don’t bring back his property!

Instructions
Get a BIC pen, the most common pen in the entire world. I personally recommend BIC fine which has a smother line than the normal ones.
Print all parts
Place the gear and stopper onto the shaft (no glue)
Glue on the mouth in the same direction as the stopper
Glue on the Eyes and refection points
Insert the assembly into the bottom parts of the body
Close it down with the top (no glue here, for potential future maintenance!)
Place the inside of the BIC pen into the new printed one