A Staffordshire twin handled frog mug, mid-19th century, the exterior decorated with hunting dogs chasing and catching game birds, unmarked, 14.5cm high The frog mug, known also as a 'Surprise mug' or 'Toad mug', was originally designed as a practical joke. The interior of the mug features a fully modelled frog which is revealed to the drinker as the liquid is consumed. The mugs were originally made in Liverpool and Sunderland, where they were much used in taverns frequented by sailors. The inspiration for this practical joke in ceramic was a more benign version of the age-old practice of slipping a live toad or frog into a fellow drinker's beer mug when he was not looking. Initially, these ceramic frogs were solid, painted in green and brown glazes to resemble a real frog as much as possible, in order to maximize the shock to the unsuspecting drinker. Over time, the ceramic frogs were often made with hollow bodies and small openings which allowed air to pass through them. These hollow frogs would not only startle the hapless drinker when they emerged from his beer, but they would also embarrass him by making various rude noises as the liquid escaped the hollow body of the frog. Victorian scholars would have us believe that barmen kept frog mugs on hand to hurry on along those patrons who had drunk too much. As they drained their mug, the tipsy patron would be confronted by ''a popeyed, reproachful frog countenance'' which was supposed to shock the inebriate and hurry him on his way home. This may have happened occasionally, but it is more likely that bar keepers kept a supply of frog mugs available to enable their patrons to play jokes on one another or unsuspecting strangers.