Falanx

In one parallel universe, Falanx was a companion of the Tenth Doctor. An eight-foot tall alien resembling a lobster, he was apparently hired by the Doctor to provide Extreme Protective Services as the Doctor travelled.

When the Tenth Doctor of the prime universe landed on Earth as it was being affected by the Continuity Cap, his companion, Donna Noble, briefly swapped places with Falanx. As the Doctor concentrated, he was able to partially change things back, briefly resulting in Donna returning with Falanx's hands and, presumably, Falanx returning to his universe with Donna's hands.

The Doctor was able to revert the effects of the Continuity Cap, setting things back to normal completely. (COMIC: The Continuity Cap)