THEME: None
After a couple of subpar days, I tore this puzzle up ... possibly because I slowed down and approached it pretty methodically. My answers washed over the puzzle from upper right (somehow got 8A: 2005's "Walk the Line" and others (biopics) immediately), and I travelled mostly counter-clockwise, til I finished up in the middle right of the puzzle (the last letter I wrote in was the "e" in 29A: Snap _____ (pea).

15A: Derived by logic (a priori)
I knew this ended in "i," and that's all I needed to know. My quick solution to this clue is one of the few things for which I can credit my mostly dreary, jargon-ridden, moderately pretentious, semi-prestigious graduate school education. Thanks, University of Michigan! I guess the 90s weren't a total waste.
19A: Actress with the memoir "Call Me Crazy" (Anne Heche)
Possibly my favorite clue / answer of the bunch. Again, the future obsolescence factor. She was famous for like 3 weeks in 1997, and only for dabbling in lipstick lesbianism. And she gets in the Times! Actually, to her immense credit, she was in one of my very favorite movies of all time: Walking and Talking, though the real star of that movie is the fantastic Ms. Catherine Keener.
22A: Film about a blind man for which the lead won Best Actor (Scent of a Woman)
Apparently this puzzle does have a theme, and that theme is: Reasons I would not willingly relive the 1990s.

33A: Kiosk item (daily)
This little clue, whose answer sits at the dead center of the puzzle, is supremely elegant and constitutes a near-perfect Saturday clue: completely unexpected answer arrived at with flawless, impeccable, unassailable logic. Sweet.
38A: Savvy film/TV characer whose name, paradoxically, is Spanish for "idiot" (Tonto)

39A: Bygone weapon (poleax)
And my nerdy childhood spent playing D & D in dank bedrooms comes in handy yet again.
50A: 1983 song that begins "Hate New York City" (I Love L.A.)
Now I should have got this right away, both because the clue points you toward the right city (LA being of course the opposite of NY), and because 1983 is basically the dead center of my database of pop musical knowledge, that being the first year of what we'll call my adolescence, the year when MTV was more important to me than food or sleep. But when you're staring at "_ _ _ v _ l a" you don't see two words and an abbreviation.

I think I also unconsciously blocked the answer to this clue because that song Sucks So Bad. To see how I feel about most Randy Newman songs, please see the relevant episode of Family Guy.
4D: Brandy cocktails (sidecars)
My favorite drink name by far. I don't think I've ever had one. I'm going to order one the next chance I get and see what happens.
10D: Council of Three Fires members (Ottawas)
Of course my first reaction on completing this answer was: how many damn Ottawas does Canada have? Then I realized that the reference is probably to a Native American tribe. And then I moved on.
39D: Wordy (prolix)
I love this answer because it sounds so much cooler than "verbose." Despite my affection for this word, I stared at the puzzle for a while thinking, ridiculously, "what's that word that means "verbose" that I like that other people don't usually know so I don't use it that often...?"
Top three things "prolix" would be if it weren't already a word:

a. programming language
b. breakfast cereal
c. Felix the Cat's wordy cousin
Signed, Rex Parker, King of CrossWorld