Gnasher

A black dog was a character in The Beano.

He appeared on the front and back of The Beano Summer Special 1981 with Dennis the Menace at Dolphinarium, a swimming pool. In these depictions, the front depicted him with Dennis on a dolphin wearing a cowboy hat labelled "JR's", and using a water pistol against a group of individuals. The back depicted them both in the air after another character held a hoop on a stick for the dolphin to jump through. (TV:, )

Other matters
Although he was not named as "Gnasher" in The Rings of Akhaten, he is named as such in the real world, and was the pet dog of Dennis the Menace.