Can I add an animation to an already made character?

So I worked on humanoid body that stays with his hands up all the time (I added the health, moving script, gun pickup/drop etc). How I want to implement the slight hand motion when standing. I exported the animation from blender to unity and when I added the animation controller to the player it does not work, but if I drag the new character from the new animation package it works. Is there a way I can apply the animation from one to another (the one I worked one has different sizes than the other one but bones names are the same) without moving all the scripts and features from the old one to the new one with the animation?