Are you seeing this in your Raw Data? Or in a custom dimension that is set to hold the URL?
If a custom dimension, technically someone could have been messing around and injected a random URL into your tracking (technically the same could be said for the raw data URL, all someone would have to do is take the tracking call and replace the value in the g parameter)
I don't know why people would do this, but we had a site a few years ago where people would randomly change the values of some of our dimensions to replace the "o" with "0"... I was a little annoying, but overall the traffic was so low it was easy to ignore and filter out.