Doctor Who: Death is The Only Answer

The story

In the console room of his TARDIS, the Eleventh Doctor is celebrating his acquisition of a new fez formerly owned by his old friend Albert Einstein. The Doctor trips near the console, knocking the fez out of his hands and onto a lever on the console. The Doctor accidentally pushes another lever, causing the fez to vanish. A time portal appears and Einstein himself stumbles through it with the fez, bewildered.