Jim the Fish
From Tardis Wiki, the free Doctor Who reference
Jim the Fish was a friend of the Eleventh Doctor and River Song, whom they met on one of their adventures. When they met him, he was building a dam. He was still doing so some time later when the Doctor checked up on him. (DW: The Impossible Astronaut)
River Song's diary contained an entry called "The Ballad of Jim the Fish." (VG: The Eternity Clock)