Barnacle
From Tardis Wiki, the free Doctor Who reference
Barnacles were creatures found underwater, known for clinging onto the submerged outer edges of boats. Another kind of barnacle, the space barnacle, could be found on the outsides of spacecraft travelling through space. (PROSE: The Hungry Night)
In the Land of Fiction, Rob Roy MacGregor returned the Doctor's TARDIS to him once when it had been lost underwater, and had been recovered covered in barnacles. (AUDIO: Legend of the Cybermen)
Donna Noble once compared an alien tourist to a "walking" barnacle, with tentacles. (AUDIO: Death's Deal)
