One of the things that actually convinced me to give the film Captain America a try was that I read somewhere that Howard Stark was in it, and I was fascinated by the idea that Cap and Tony's dad worked together. There are so many intricate little connections you can make with that, and of course fandom has done a wonderful job playing with it -- in some stories Tony grew up constantly hearing about Captain America, and in others he used to search out little tidbits his father didn't want him to know, and in others he didn't know about it until he was grown. And of course Cap meeting Howard's adult son, he gets to compare the two men and learn about what changes came over his friend, and Tony sort of stands as his one link to his former life, however weak.