Artist Mel Stringer decided to fill her pet pug Grover’s playpen full with plastic balls and his favourite toys to see how he would react. As this cute and colourful footage shows, Grover certainly enjoyed the experience. He runs around with carefree abandon, jumping over and into the balls, getting plenty of pulsating exercise along the way. His fun has proven a viral hit, attracting over 140,000 views in the first two days of being uploaded. Credit: YouTube/Mel Stringer