Five O'Clock Shadow

The Five O'Clock Shadow was a malevolent incarnation of all the grim responsibilities of life from which the Doctor always ran — a temporally-anomalous, sentient manifestation of his every anxiety.

The Shadow was first trapped by the Doctor in a single instant of time — exactly five o'clock, hence his name. He escaped from this prison when the Doctor's TARDIS, through a bout of bad luck, became stuck at precisely five o'clock. Breaking through the bars of its prison, the Shadow menaced what he thought was the Doctor, only to realise he had been tricked: he had no power over the Doctor to whom he was talking, Dr. Who, a sentient mathematical projection of a perfectly happy and whimsical Doctor. The Doctor had created Dr. Who to distract the Shadow long enough to fix the TARDIS, and the Doctor took off with Dr. Who and Suzy, leaving the Shadow stranded in a frozen instant once more. However, the Shadow chuckled as the Doctor left, knowing that he could not run forever and would have to face death, strife, and loss someday. (POEM: The Five O'Clock Shadow)