Ian picks up a lot of stuff from books and TV. He's famous for picking up phrases and using them in conversation (but apporpriately). For example, he'll say things like "last but not least" or "dead as a doornail" (from the True Story of the Three Little Pigs and the Big Bad Wolf).
Tonight, Ian has a slight fever. He asked me if he was going to get the flu. I stopped and wracked my brain - had we discussed the flu? Where was that coming from? I asked him, and he said, "like Rosie". Then it hit me that Rosie, on Calliou, had the flu. He then told me that he would have to "stay in bed for a few days" if he had the flu, just like Rosie.
Wow. Too smart.