Sometimes, the best way to respond to a tweet on Twitter is in animated glory – GIF animated glory that is. Twitter has now enabled Animated GIF support on the web and iOS/Android apps. You’ll find that GIFs show up just like Vine videos, with a play button on top. You’ll have to push that play button to start the animation.
— Twitter Support (@Support) June 18, 2014
Of course, support for GIFs was probably a very highly requested feature since GIFs are fun and there is almost a GIF for everything. So get on it, reply to your friends with GIFs!