The San Diego Zoo's panda cub, Xiao Liwu, was eager to play with a plastic ball during his 18th exam this morning in San Diego, California, Dec 18, 2012. Panda keepers gave the cub the new toy to test his coordination and encourage him to play with new objects. The 20-week-old panda weighed 14.5 pounds this morning when he was brought in for his weekly veterinary exam and is on track with other giant pandas born at the San Diego Zoo. [Photo/Agencies]