Historical clue formulations

• Mischief-maker — 2021-07-07
• Scapegoat for many a failure — 2014-06-13
• Mischievous one — 2009-05-17
• Imp — 2008-02-03
• Unseen troublemaker — 2001-12-28
• Invisible troublemaker — 1997-10-27