clever monkey
A person who acknowledges, accepts, and is required to perform a simple, direct, tactical job task but continuously overthinks, complicates, and needlessly over-analyzes the task as to leave the task 1) incomplete and/or 2)grossly incorrect and assuredly causing much consternation, gnashing of teeth and other colleagues to complete the task correctly.
Patrick always felt he knew better than everyone else and, behaving like a clever monkey, independently created his own invoice format to bill customers in Comic Sans font with his favorite, grossly inappropriate 'Quote of the Day' in the footer.