Since Animal Crossing has retired him, Mewgenics is picking up the slack with its own Mr. Resetti-like being to heckle you for save scumming.
Mewgenics is tough. You could be having the playthrough of your life and then one bad move during a round could send your run to the depths of hell. Since the game doesn't save during battles, you may be tempted to save scum so you get a fresh start. But the developers foresaw this and prepared a surprise for those who do, which will immediately bring you back to the days of Mr. Resetti chewing you out in Animal Crossing.
Once you return to the game, Steven from Edmund McMillen's previous game Time Fcuk – who also had an appearance as a boss in The Binding of Isaac and as a bonus level dealer in The End is Nigh – will arrive on screen and berate you. That guy is not happy. He will threaten to crawl out the screen and kill you, and he will say naughty words to you. However, you can safely save scum once per run, effectively giving you a free reset in one battle.
The next two times you save scum he will inflict ailments onto your party and make your run that much harder, but it's the fourth time that's the real kicker. Once you quit during a battle four times Steven will appear again, except this time he's not angry, just disappointed.
He will calmly say "Yeah it's over, give me the controller…" and for the rest of the run Steven will control your cats during every battle. It's not even in a way to screw you over. Steven is pretty good at Mewgenics, and you can save scum forever from that point on if Steven isn't doing too hot (although he seems to play the battle out the same way every time).
Psst. I wrote a savescumming in Mewgenics guide that will tell you how to use it effectively, you should check it out… just don't tell Steven.
