For example if i want an npc to get angry at the player, and he yells something like "You idiot!" and when he says that i want to give him an animation where he actually looks like he's yelling.
I know how to change animations outside of dialog but i'm not sure how to do it inside dialog.
You would do it the exact same way you would outside of dialog. You can place any code inside dialog, you just need to indent it so that the game recognises it as normal code, rather than as part of the dialog script. :)