https://media3.giphy.com/media/hD1anr83g7PlS/giphy.gif?cid=ecf05e474d40c3079959e3f35c5e6a3e059fc13a077224fe&rid=giphy.gif
To display the .gif in your reply, you sandwich it like this:
<img src="the address of the picture " plus something to control the size>
or in this case
<img src="https://media3.giphy.com/media/hD1anr83g7PlS/giphy.gif?cid=ecf05e474d40c3079959e3f35c5e6a3e059fc13a077224fe&rid=giphy.gif" width=40%>
where the width=40% tells the computer, "You know whereever the display area is you're showing this picture on? Well, make the picture 40% of that width."
And the result is
Meow.
Many emojis, you can display like that, you just have to find an emoji you want, and right-click on it "Copy Image Address" and use that instead of the leaping cat. But beware of the size, just play with it.
Thanks!