Can 3D printer models be used in video game engines and vs versa? If someone creates a 3D model of a character for 3D printing can I import that model into Unreal engine or Unity 3D for use in a video game? Also is the inverse true? Can I get 3D model of Mario and send that to a 3D printer?
Specifically, it’s more important to know if I can pull a 3D printer model into an unreal game project
Yes. You can import it into Blender, but it will need &quot;bones&quot; and &quot;armature&quot; if you want it to move at all.   In Blender, you can manually add armature and &quot;Rig&quot; it, if you want animations.
You can probably convert whatever file type the 3D model is (probably STL) to fbx with Blender
For animating, start with a super basic 2-bone rig YouTube tutorial, then learn about vertex weights or automatic weighting.
But you'll have to UV map it too. The UV map tells textures where to go on the model, STL doesn't have those.
Your time is 100% better spent finding a model that's ready and moving on with your project.
Check Unreal Marketplace.
Also,
https://www.turbosquid.com/3d-model/free/low-poly/character
https://www.cgtrader.com/free-3d-models/character?polygons=lt_5k