You've probably seen this article, but...

[sarahenany.livejournal.com]

...it offers such a great, great analysis of, and tribute to (dare I say fanboying of?) I Spy  that I thought I'd risk duplicating.

This is the URL:

http://www.popmatters.com/pm/column/123855-robert-culp-from-i-spy-to-hickey-boggs

And since you can never be sure when pages will be taken down, I've included the text of the article behind the cut. (Why yes, I'm totally paranoid and mistrustful of the Internet. Why do you ask?) ( Full text behind the cut if link should break... )