MPPs are not the same as MLPs
They don't have any markings on their hooves, they are just hard plastic with hair. The brown ones can have some variations in paint. To my knowledge there are no MPP fakes, I've never seen or heard of one (I don't think it was big enough to consider cashing in on for other brands, plus there wasn't an obvious gimmicky gimmick like MLP with colors and symbols.) Unless there are noticeable differences from ones you have seen, I highly doubt it's a fake.
Here is the wiki page if you would like to take a look.
Congrats too, they are a bit hard to find and $5 is a steal!