Sense patrol!

I heard Young MC's "Bust a Move" on the radio the other day, and the following verse has not left my head since:

Your best friend Harry has a brother Larry;
In a week or two he will marry.
Try to make the wedding if you can
For at the ceremony you're to be the best man.

There is much here that doesn't add up. Every line suggests that the second-person protagonist's relationship to the groom is minor. In the first line he has to be informed of Larry's existence; in the second he is given only the vaguest possible information concerning the scheduled date of Larry's nuptials, and indeed learns of them only a few weeks prior to the event itself; he is not even urged forthrightly to attend, but only to try to attend if his schedule permits. And yet, we learn at the verse's conclusion: He is to be the best man? Does Larry have no friends of his own, forcing him to draft his brother's best friend? What about Harry himself? Have things between the brothers reached the point where Larry doesn't feel comfortable asking Harry to stand up for him? I can only hope that my social life and my relationship with my estimable coauthor never come simultaneously to such a pass that I find myself placing a long-distance call to Robin Mulder and saying, "Listen, there's something I wanted to ask you...."