I had to join this site to reply because the exact same 2 movies showed up in my purchases just the other day and I have never purchased a movie on youtube.
I checked my bank accounts and there are no signs of any purchases, and I checked this Google wallet page and I don't even have a credit card signed up for the account, so this is obviously some sort of mishap.
I just assume don't watch the movies or that may lead to some sort of charge.
Edit:
Right after replying, I remembered that our class used the Nexus 7 in our computer science class on friday, and I wasn't doing the assignment, I instead signed into google and downloaded angry birds.
I am now actually thinking that these are free movies that sort of come with the Nexus for free, but I am still afraid to watch them because I don't want to pay $18