I found it on someone's blog, I guess it was this one: http://triplebagel.tumblr.com/
(the comments are pretty funny BTW
) That was a gif and then I can't remember how I found the actual video...
It's pretty difficult to find, you can't access the video unless you have the link, because it's not referenced in Youtube search (don't know why, maybe it's meant to be only for really dedicated fangirls!)
I think it's probably an ad for tennis on ESPN. Those guys sure know how to advertise their sports channel