The Karsudan was a colony ship. It launched in the 40th century, but a malfunction kept it from its destination for over three hundred years.
It sent out a distress call that the Fourth Doctor, Romana II and K9 Mark II answered. The ship was infested with mice, descendants of the pets brought on board by Bertram. In addition, a collision had busted a hole in the ship. The Doctor and his friends repaired the ship and set it on its way, to wake up its passengers on Christmas. (PROSE: All Snug in Their Beds)