As is often the case with early-week puzzles, I didn't know what the theme was while I was solving, but now that I understand it, I like it. It's absurd and goofy, and, well, that's often enough for me. QUESTIONTHEDUCK (36A: Try to find out what's what at a pond?) made me laugh. Not "out loud," but still, I think I might have exhaled slightly harder through my nose. Does that count as "out loud?" I guess it was audible, within a certain radius...
In non-theme fill, I started entering "U.S.S.R." for 1A: Letters on Soyuz rockets (CCCP), but caught myself before I had even finished, and put in the correct answer. After that, almost everything went right in until I got a little more than halfway down. TEFLON (44A: Polytetrafluoroethylene, commercially) took a few crosses, and the same is true for ALTER (48D: Take up or let out).
Favorite clue, and best of the week, so far - 35D: It's all around you (SKIN). Eeewwwww! So gross, but so good. Also, speaking of the body, I thought it was a good clue for ULNA today (14A: Fifth-longest bone in the human body). 15A: One navigating the web? (SPIDER) was cute.
You might be interested to hear that I looked up "swab" as used in DECKTHESWAB (56A: Kayo Popeye?). It is slang for sailor, of course, and it's not far from "synecdoche." Heh. I've heard "swabbie" more often, but my "work" dictionary (a gift from Frannie when I got my new job!) says that "swabbie" can be used for anyone enlisted in the U.S. Navy, and that "swab" is specifically for a sailor. I don't know about that, but I guess I'll have to take Webster's word for it. And I suppose "Kiltie" can be used for any Scot? (2D: Kiltie's group (CLAN)). Webster does not agree. The only definitions they give are "n. 1. A flap of fringed and, sometimes, perforated leather extending from and folding back over the top end of the vamp of a shoe 2. A shoe with such a flap." I'll have to try that when we go to Scotland in a few months. "Hey Kiltie, got any scotch for me?"
Not perfect (STANDEE is poor), but fun enough.