I really clearly remember Benedict struggling with pronouns one day. He wanted to say something about what he was doing and what I was doing but kept saying you when he meant me, or the other way round. He could tell something wasn't right, and was frowning with concentration over it, but it just wasn't coming out right. (I think I tried to help but wasn't very effective at it, which was probably just even more frustrating for him and for me, which is probably why I remember it so clearly.)