Do you mean the gestures and emotions that you can make your player character do? You unlock those once you unlock Club LOL. There's more information on Club LOL and Dr. Shrunk elsewhere, but that's what to search for if you want more information about that.
And if that's not what you meant, then I'm not sure what you mean. ^o^;>
Like kiwi said, you can do emotions (or jokes as they're called) after unlocking ClubLOL each day, if you bring Shrunk a snack before nighttime, I think it's anytime in the afternoon, like after 12-1pm and before 6 or so when the club opens, but you give him a snack and he'll tell you a "joke." This will be added next to your text tab at the bottom of your screen and you can use it to do the emotions and dances or movements from there by clicking the icon of the one you want to do!
If you're talking about people that do the "bug-bite" movements, or the fainting, those are hacks.
Or are you talking about snippits from the game in someone's signature?
If so, I think you need a capture card to do it? Then theoretically you would have to convert it to GIF, but I'm sure someone else on the forum knows about this whole thing better than me ^^; hope you get your answer!
(ノ◕ヮ◕)ノ*:・゚✧