I don't want to be discouraging... but...
If you're asking "is it possible", then of course the answer is "yes". Several NES games have animations, so there's no hardware limitation that says animation is impossible =P
If you're asking "is it a lot of work", then the answer is also "yes"
This is one of those things where if you have to ask how to do it, you probably aren't able to do it. You're talking about injecting new graphics and entirely new drawing code to display it. This will require a pretty solid understanding both of how graphics on the NES work, but also how the actual games works as well as how to actually write and insert new code into the ROM. This is just about as advanced of a hacking task as you can get.