I guess I started Dad-Trolling Katie when she was pretty small.
Evidence: I remember the first time we went to a pet store and I showed her the hamsters. She didn't believe me: she was firmly convinced that "hamsters" were something I'd made up. I finally got a clerk's attention and said, "Tell her what kind of animal that is"; he gave me an incredulous look and said, "It's a hamster!"
Much later, I tried to convince her that molasses wasn't vegetarian—since, obviously, it's made from the rear ends of moles. Nope, she didn't buy that, but she did try it on a few of her friends.