In his article on the essays of Zadie Smith in the latest New York Review of Books, Michael Wood writes that "in an epigraph she quotes Katharine Hepburn alias Tracy Lord in The Philadelphia Story: 'The time to make your mind up about people is never!'" Let me start by saying: great movie, great line. However...
Well—hm, O.K., this might be difficult to get across. Let's see here. Don't worry if it's hard to follow; you'll get it eventually.
Katharine Hepburn is an actress, see?* And Tracy Lord is the name of a character she played in a movie. With me so far? So, first of all, "Tracy Lord" is not in fact an alias for Katharine Hepburn. And, second of all—here's the really tricky part, so get ready—the line being quoted should not be attributed to Katharine Hepburn, not even under any of her many aliases.
The line in question is something that Hepburn delivered from a screenplay (which she herself did not in fact write), and that screenplay was based on a play; we can assume that the line being quoted is not by her but rather by Donald Ogden Stewart or Philip Barry—maybe Waldo Salt, according to the IMDb. You might even make the case that it would O.K. to credit the character she played, Tracy Lord (who is a fictional character, remember, and not simply one of the famous actress's pseudonyms). But Hepburn herself? No.
Another of Hepburn's many aliases.
I know this is hard. But once you wrap your mind around it, folks, you (and we!) will be able to step into an exhilarating world in which actors are no longer given credit for the lines they memorized, in which finally the distinction between fiction and reality becomes clear, in which it is understood that actors are only pretending to be the people you see on screen!
No, no, wait! Wait, don't get angry at them! They're doing it for your entertainment!
O.K., a little too much too soon. You sleep on it and we'll talk more in the morning.
* Some people just use the word actor regardless of sex, but that's not important right now—I don't want to confuse you.