My daughters are like polar bears.  Hiking somewhere near Lake Tahoe, they came upon one of the many small lakes hidden in the mountains, prompting them to strip down and swim in the frigid waters out to the middle, where a mini iceberg was floating, and they proceeded to sit on said ice, freezing their behinds, before jumping back into the water.  My original thought for Kristi's birthday card was to draw a penguin on an iceberg to commemorate their little adventure, but since this was in Tahoe, I decided on a beaver as though his little dam/house had frozen over, and sunshine rhymed with her age of 29.