In the WWDC 2015 fox demo, there is a SCN file representing the 3D fox. If you want to incorporate the fox in a different app, you import the fox's SCN file and its texture maps.
But if you have 3D characters made in an authoring program like Cinema 4D (https://www.maxon.net/en/products/cinema-4d/overview/), how do you generate similar SCN files for the different characters? Cinema4D cannot export SCN files like this so what do you do?
And does the process change if the characters are animated?
I'm using C4D r12, I imagine the process should be the same for later releases.
One option is to create a separate file for each character. Pay attention to the organization in the Object Manager: the hierarchy of objects as listed there will be the scene graph of nodes in your imported scene file. This includes nulls which will end up as container nodes in SceneKit. The names of your objects and nulls in C4D will be the names of the SCNNodes in the scene file. When you have this set up as desired, save via File > Export... > COLLADA(*.dae)
Alternatively, you could create all your characters with one file and then parse them in SceneKit using the unique name of that character's container node (previously a "container" null in C4D).