The quotation by Samuel Butler fits nicely with this video of an elk calf frolicking in a puddle.
Via Joanne Casey's I Have Seen The Whole of the Internet.
Originally posted two years ago; now updated to add this video of interspecies play:
"Every evening a river otter comes to play with our daughter's dog Rio. What was once an acquaintance on the other side of the fence has now become a friend who comes to play through the fence.It has been interesting to watch as their trust of each other has developed over the past several months."