The Disco/Fires do have what seems to be multiple ringers, that's what leads me to think that's what's happening here. I'm not 100% sure though, that's why I have to wait to see if someone can duplicate it with a confirmed Disco and a Mojo.
I suppose it is possible that one could be a het pied, but neither of the parents were bought as such.
Exciting and frustrating at the same time, right?