It did kind of come out of no where. However I sldo sppreciate that it was subtle. Maybe the problem was that it was too subtle...hmm...

I didn't see any problem with the entire Caspian's Father part, it wasn't a huge part of the movie.
As far as when his father appears on the DI, I think that it was quite logical for the mist to want to tear him down by making him think that his father was disappointed in him. Seeing as he hadn't seen him since he was a small child he would like to know that his father would be proud of him, who wouldn't?

And at the end of the world any good son would like to be with his father, especially if he was murdered when you were very small. And seeing the way he reacted in PC when he learned of his murder they were probably very close.

I thought it was a nice idea, but underdeveloped. However, the entire film is underdeveloped so this didn't really stick out to me as not being very good. I thought there was more to it than the Rhince and Gael storyline actually because Caspian has been hearing things about his father his entire life. I don't think it was there as much as it should have been since there was that big moment at the end about it, but every single plotline in the movie had this problem.