I would say no if you have had it in the fridge for a few days. If you thaw it out, offer it to your snake and he refuses then its ok to refreeze it if you refreeze it right away. I have heard of people refreezing once or twice even. Im not saying i would definetly do this, but i would certainly hate to throw out a perfectly good rat. I mean what if you have like 10 snakes and half of them refuse? Youre gunna waste five rats and just chuck them. That means their deaths were pointless. I would feel sorta bad about this personally. Just my 2 cents...