If you have wonder why animated gifs don't work after being upload in a blogger post, I think a can give you a quick answer to this question.
When uploaded in a Blogger post, the animated gif having a gif extension is changed to a png image. So, if your image was named moonwalk.gif, it will be named moonwalk.png after being uploaded in your Blogger post editor.
To show a working gif animated, just upload your picture in another host and put the link in this code :
<img scr="http://yourhost.com/yourimage.gif" alt="picture, keys, words"/>
Put this code in your post and you'll have a working animated gif in you blogger blogspot post.