The first pope was a Jewish "spy"?

I have a rabbi who told me that there is a censored Rashi in avodah zara that makes the claim that Peter (the first pope) was actually a devout Jew, even after he became the pope, and he attempted (succeeded?) in steering the burgeoning xtian religion away from Jewish practice and belief, in order to make it less appealing to Jews. Has anyone heard of this before? Crazy if true.