Sonny (Clara Oswald and the School of Death)

From Tardis Wiki, the free Doctor Who reference

Sonny was the nickname assigned by the Twelfth Doctor to a Swordfish bar-trophy which he rescued from The Slaughtered Whale, a bar on Earth occupied by Sea Devils disguised as humans.

He used the fish to block a barrage of weapons thrown telepathically at him by the creatures, and grew fond of the fish afterwards. Later, he introduced the fish to Clara Oswald, describing it as "our new companion", and as "a character [with] a cutting intellect and a razor-sharp sense of humour".

As the Sea Devil plan collapsed, the Doctor duelled Mrs Mariner atop the crumbling Ravenscaur School, Sonny being impaled by the Sea Devil's trident. When the Doctor turned the Sea Devils' sonic devastators onto Raven's Isle, Sonny fell into the collapsing mass. As the Doctor and Clara flew away in the TARDIS, the Time Lord mourned his short-lived companion. (COMIC: Clara Oswald and the School of Death)