I get quite a few anomalies from a strain of platinum ribbon tail guppies I keep. Not sure why but guessing it’s due to the complicated genetics used to create this fish? I dunno but I always get some doubles like yours in all variations with each batch of fry. Mirror image, sideways, just the heads, etc but none of them ever survive long or are culled asap. That’s odd to see one full grown. Kinda gross to be honest...you gonna keep it?