Possible Clues:

• Krypton, for one
• Neon, for one
• Xenon, e.g
• It's hard to get a reaction out of it
• He is not moving - how amusing is that?
• Noble thing
• Passive element in the helium group
• Unreactive 'noble' element, such as argon
• Helium or argon, which could be angriest?
• Eg, helium, xenon etc.