Your gif may be too big, there is a 2mb file size limit (and it works better if the gif is smaller than that). Also, most of my gifs are smaller than 400 x 400 px, this one by pusheen is only 250 x 250 px and 51.8 kb.
How did you add that gif in your last post? When I try it, it only shows a grey polaroid.
I-want-my-IWTV 