Talk about wacky! This was so over the top silly, I loved it. First off, having four 15-letter original palindromes (well, after googling all four, I see that the last two are at least searchable) is crazy. And I am still giggling over numbers 3 and 4. TOOBADIHIDABOOT! NOWAYAPAPAYAWON!!!!!
Okay, so your mileage may vary on this sort of thing. I personally enjoy the silliness. I also kind of enjoyed being able to work the back of the long answers after figuring out the crosses of the front parts.
There are some good stuff in the fill, and some... well, questionable parts. I'll start with the latter. Jesse UNRUH? The loser of the 1970 gubernatorial race in California? Apparently, he was known as Big Daddy Unruh, which wins for the best nickname. Not only did he lose that race, he also lost several other races, before becoming the State Treasurer of California for over a decade. I'm going to go out on a limb and say that's a stretch for common knowledge.
1A: Music direction meaning "with the bow" (ARCO) is good (A-). I always enjoy musical answers. It was also the first answer I put in confidently.
12D: Second cousin? (MOMENT) is a very nice clue. It took me quite some time to recognize what they were getting at there. 13D: Time out? (SIESTA) was not quite as good. But I liked 39D: Where some long runs take place (BROADWAY) the best. Hurray for the no question mark clue!
Anyway, this was fun, and I give it a thumbs up.