Definitely some type of ground squirrel, but I'd guess something smaller than a marmot (which is just an overgrown ground squirrel, really):
LOL pic
marmot -- too broad in the skull
golden-mantled ground squirrel -- a candidate
Columbian ground squirrel -- another, especially given the background scenery

and, googling deep enough, I find the origin of the LOL pic, labelled as being a Columbian ground squirrel:

original National Geographic photo of the day page
CBC "Scene-stealing squirrel crashes Banff tourist photo"

The next candidate for a viral photo:
dog yawn

O.k., yeah, there are other important things I should be doing... even if it is Sunday afternoon!

~ Becky in Tucson