You know, being INFP does not mean you are depressed, or sad, or you lock yourself away from humanity, or that you are grossly self-absorbed, or any other negative stereotypical trait that one associates with INTROVERSION.
I have had some confusion in the past over my own INFP/ENFP-ness, because I can be / appear quite social, and I love hanging out with people. But people drain my battery, not recharge it, and there's nothing I've ever done in my whole life that has changed that. There's a fundamental difference between types that I think it is important to respect. Saying an ENFP has an INFP locked inside is implying that an INFP is somehow smaller than an ENFP. And that "INFP" is the dark, bad side of being "ENFP". And wow, I really can't agree with that.
How about this - when I have a drink or two, I let out the ENFP locked within me. Doesn't that sound as improbable as the OP?