with over a million different drawings of the ponies including references and crossover, there is always a high chance of people doing the same concept withouth knowing somebody did it before, plus, if somebody makes a certain crossover, based on a movie. and another one does that later, that person is not stealing the first one's Idea, They are using something that existed before the first artist even made it.

would you report ambrose for drawing something star wars did ? No, you wouldn't. so why report this artist for using the same concept , yet happens to be the second. third or whatever number of fan art ?