I just rewatched Smoky (as much for the "They still wear shoes, right?" line as for this ;) ), and Dan also says that he met Lisa at 19 and married at 23. However, I can't remember which season it is that Casey says he's known Dana for 15 years. If it's not until the second season, then they met at the same time, I guess. I feel like it would be a big difference if Dana had known Casey a year before he met Lisa, though.

Also, I spend a lot of time wondering what person named Lisa did something to piss Aaron Sorkin off so much that all his TV show exes get that name. It sort of amuses me. ;)