Three Point Plan For Getting Jon To Stab Himself In The Thumb:
Step 1: Get him to step in some kind of sticky, crusty candy (Just throw it anywhere on the ground; he's bound to step in it. He is Jon, after all.).
Step 2: Wait for him to notice (It'll happen eventually).
Step 3: Sit back and watch as he tries to scrape it off his shoe with his pocket knife and nature takes its course.