I know that mine always liked comic books with girls that had big boobs. I have his whole collection of them in my closet & I even bought him some of the ones he was missing so he could complete his collection. The zombie stuff is a little out there, but I wasn't the least bit surprised when he showed it to me. Nothing surprises me now though.
I totally hear ya on the schoolboy fantasy/exploration bit. He even asked if we could have a quickie in the backseat in a parking lot one day. A few years ago, I mentioned it would be fun to go "park" on a gravel road just for the fun of it & he told me we were too old for that, but NOW it's ok? What's funny is that I told him I'd think about it and he was all excited that I didn't say no...and then he never brought it up again. Had I said no, he'd have pestered me all day about it.
I also agree they want to try out the new stuff they are learning with OW and see if we like it too. Mine has always been that way though. He has a whole video collection and thought we could watch & do stuff, but that just doesn't do it for me. I told him way back that I'm no porn star & I want romance, not just crazy sex. I think OW gives him the crazy sex he always wanted. To each their own I guess. That will get boring to him too, as she will eventually run out of things to show him and he's not one to come up with this stuff on his own.