Historical clue formulations

• At the drop of ___ (instantly) — 2021-04-05
• At the drop of ___ — 2016-03-23
• "The Man Who Mistook His Wife for ___" (1985 best seller) — 2014-05-04
• Answer to the old riddle "What lies flat when empty, sits up when full?" — 2011-06-05
• At the drop of ___ — 2010-06-01
• Pull out of ___ (produce suddenly) — 2007-10-19
• "___ Full of Sky" (2004 Terry Pratchett novel) — 2007-06-02
• At the drop of ___ — 2005-10-20
• "I Had ___ When I Came In" (old Irish tune) — 2005-03-26
• "The Man Who Mistook His Wife for ___" (Oliver Sacks book) — 2004-11-28
• At the drop of ___ — 2004-11-22
• At the drop of ___ — 2004-01-06
• At the drop of ___ — 2003-11-11
• At the drop of ___ — 2001-04-24
• "The Man Who Mistook His Wife for ____" (1985 book) — 1995-10-18