Prior to Gify and The Office if you wanted to post a reaction gif you would have to choose from your selection of existing ones. There were ways to make gifs using photoshop and so making a new one was a bit of an artform, especially squeezing out the proper quality and framerate. It was a craft, and sometimes an artform. Now reaction gifs are just 3 second clips of The Office where Jim Halpert stares at things