The Cubes come to life (the Birdy Song)
The Doctor and Amy are summoned to the UNIT headquarters under the Tower of London where a Kate Stewart shows them several cubes under investigation, every single one behaving in a different fashion. The Doctor recalls his friendship with Kate's father, Brigadier Sir Alistair Gordon Lethbridge-Stewart.
The Doctor Kills Some Time
Mysterious cubes have appeared all over Earth. The Doctor is naturally very curious, but after the cubes seem to be doing nothing, he gets extremely bored. Amusing clip from series 7 episode The Power of Three.