Humpty Dumpty
From Tardis Wiki, the free Doctor Who reference
Humpty Dumpty was an Earth nursery rhyme. Shortly before the Sontaran invasion of Earth in 2009, UNIT Private Harris told General Staal to "stop playing Humpty Dumpty". (TV: The Sontaran Stratagem)
The Ninth Doctor called the Lect Humpty Dumpty. (COMIC: Weapons of Past Destruction)
Jo Grant recited this rhyme to counter the Master's hypnotism.[source needed]
Behind the scenes
According to The Brilliant Book 2012, a book that contains non-narrative based information, the story was inspired by the Sontaran, Strax, when he met the Doctor.