Greg's love for porn is no secret; remember when he and Nick found old magazines in the desert and he was shocked people would throw them out, because those mags were 'heirlooms' and 'supposed to be passed down from generation on generation'? :-D
Oh and only last week he wasn't hiding how he was enjoying the evidence of the web-porn-peeper. *ruffles his hair*

So I'm guessing the deep dark secrets Nick mentioned are his, not Greg's *grins*.