> For example, what if you want to add custom animations any time your `Character` takes an action?

What's wrong with this?

    class Character(PhysicsobjectMixin, FightMixin, TalkMixin):
        def attack(self):
            # custom attack animation here
            return super(Character, self).attack()

        def defend(self):
            # custom defend animation here
            return super(Character, self).defend()

For me, it's still clear that 'attack' and 'defend' extends the funcionality of the 'FightMixin'. I can see even the first glance, those are inherited methods, because they use super() (call parent methods)

> How about if your physics for a `Projectile` are different than for a `Pickup`?

You need to implement two classes anyway. I see two possibilities:

I. If you have to implement this kind of different physics behavior only for Projectile. (Maybe you don't even need a mixin.)

    class Projectile(object):
        def update_physics(self):
            pass
        
        def apply_konckback(self, force):
            pass

        def get_position(self):
            pass

II. If you have more Projectile-like objects, but they are not all the same.

   class FastMovingPhysicsobjectMixin(object):
        def update_physics(self):
            pass
        
        def apply_konckback(self, force):
            pass

        def get_position(self):
            pass


    class Projectile(FastMovingPhysicsobjectMixin):
        pass

    
    class Arrow(FastMovingPhysicsobjectMixin):
        pass

> What if your character suddenly picks up a Sling of Thrown Voices, and needs to apply conversation snippets to its projectiles?

Is this a weapon which doesn't shoot projectiles, but make damage with voice or what? :D Then I think it's totally different, because if Character can have all kinds of different weapons and those behave different ways, mixins don't fit here. I would rather implement that like this:

    class Sword(object):
        def attack(self):
            # swing

        def defend(self):
            # defend

    
    class SlingOfThrownVoices(object):
        def attack(self):
            # shout loudly

        def defend(self):
            # pssszt, be quiet
    

    class Character(PhysicsobjectMixin, TalkMixin):
        def __init__(self, weapon):
            self.weapon = weapon

        def attack(self):
            # custom attack animation here
            self.weapon.attack()

        def defend(self):
            # custom defend animation here
            self.weapon.defend()

then weapon can be instance of either Sword or SlingOfThrownVoices. Note that Mixins are still in use and no complicated inheritance problem occured even if you have hundreds of weapons.