In this new Funny or Die sketch, Zac Efron [1] gets a few acting pointers from his Dirty Grandpa costar Robert De Niro [2] — or so he thinks. While a gullible Efron tries to make sense of the greater complexities of spicy versus regular mustard, he completely misses that De Niro is just using him to make a sandwich. Well, it's a good thing he's so attractive [3]. See the funny video above, and then check out the trailer for their new movie [4].