 English toy spaniels remained popular enough during the 18th century to be featured frequently in literature and in art . On Rover , a Lady 's Spaniel , Jonathan Swift 's satire of Ambrose Philips 's poem to the daughter of the Lord Lieutenant , describes the features of an English toy , specifying a " forehead large and high " among other physical characteristics of the breeds . Toy spaniels and Pugs were featured in both group portraits and satirical works by William Hogarth . Toy spaniels were still popular with the upper classes as ladies ' dogs , despite the introduction of the Pug ; both Thomas Gainsborough 's portrait of Queen Charlotte from 1781 and George Romney 's 1782 Lady Hamilton as Nature feature toy spaniels with their mistresses . The toy spaniels of this century weighed as little as 5 pounds ( 2 @.@ 3 kg ) , although they were thought to be the dog breed most prone to becoming overweight , or " fattened " . 
