Animation/video files supported by unity

So, I want to import an animation sequence i made outside of unity. I have a rendered video with a solid background, and an animated gif. Can unity some how get rid of a solid background color and play a video with transparency? or am I better off using an animated gif (if animated gifs are supported)?

thoughts or any other way to attack this problem?

Well if you use the free version of unity a video file won't work as i discovered myself too, i don't know how this applies to gif's but that you can try but a video won't work. when u use pro i would suggest video since that looks alot better. Good luck