So, I was just casually making Kingdom Hunter and I changed the skybox to some random material, and this happened.
Here is a little pic
made a little video to show more
Some one forgot to clear the buffer.
Woah, you messed it all. 
I fixed it now but pretty unusual eh!!!
Not really. 
All it is is the camera not being told to clear pixels that aren’t being drawn to on the current frame.
Well, why did that happen, never happened before.
Probably something to do with the “random skybox material”.