Copper's hunch

On 27 July 2012, the Tenth Doctor playfully referred to Rose Tyler's deductions while analysing the scribble creature as a "copper's hunch". She had deduced that Chloe Webber, a girl who'd caught her attention on Dame Kelly Holmes Close, had something to do with the creature, saying the scribble might have been a mistake drawn over by a child. They went to her house to investigate. (TV: Fear Her)