Baskerville Hound

From Tardis Wiki, the free Doctor Who reference

Being on the trail of the Baskerville Hound was one of Sherlock Holmes's most famous storylines as a fictional character. When First Doctor and his grandchildren John and Gillian came across the version of Sherlock Holmes who inhabited Storyland, he was once again on the trail of the Hound. (COMIC: Nostalgia Corner)