Death Is the Only Answer (TV story)

Plot
When the Doctor is reunited with his Fez, he trips over onto the console, knocking off his Fez and hitting a lever. The Fez vanishes and Albert Einstein arrives, with the Fez on his head. He was working on his time machine, and he thought he'd found the vital part of it- Bionic Fusion Liquid. But it wasn't, and Einstein had got it wrong. When he walked away from the console, liquid spat up at his face, turning him into an Ood. The Doctor managed to turn Albert back into his normal self afterwards, and stopped him from feeling sick with help from the Sonic. The Doctor dropped Albert off in 1945, and the Doctor and his Fez went off to another adventure, a bit of goo left on the floor.

Cast

 * Eleventh Doctor - Matt Smith
 * Albert Einstein - Nickolas Grace
 * Ood - Paul Kasey

Continuity

 * Albert Einstein gets turned into an Ood. Their last appearence was in DW: The Doctor's Wife.
 * The Doctor mentions that Einstein's toothbrush was destroyed by the Daleks.
 * The Doctor states that "This old Trash will be around until the end of time. In fact, it was."