Standing Ovations: Notice that each theme clue is a two word phrase where each word contains two OOs. Also the theme clues are Down, so that the double OOs are "standing".
3-Down. * Pasta-shaped colorful foam float: POOL NOODLE.
9-Down. * Totally chill: LOOSEY GOOSEY.
21-Down. * Celebratory search engine logo: GOOGLE DOODLE. Here's a Google Doodle from last week:
25-Down. * "So awesome!": TOO COOL.
And the unifier:
31. Enthusiastic audience reactions, and a feature of the answers to the starred clues: STANDING O'S. Sadly, I am not as clever as my fellow commentators, so I do not know how to add color to highlight the grid. Thus, I can not accent the double Os, so I'll insert the grid here so you can look for all the standing Os.
Across:
1. Deeply engrossed: RAPT.
5. Played music at a dance club, say: DJ'ED.
14. "The Time Machine" race: ELOI. These fictional post-human beings from the 1895 novel, The Time Machine, by H G Wells (né Herbert George Wells; Sept. 21, 1866 ~ Aug. 13, 1946) used to make frequent appearances in the puzzles. We haven't seen them in a while.
15. Slippery: EELY.
17. Many many: A TON.
18. Call on the carpet: TAKE TO TASK.
20. Triangle or quadrilateral: POLYGON. A Polygon is a plane figure with at least three straight sides and angles, and typically five or more.
22. Holds a grudge against: RESENTS.
23. Fed. ID fig.: SSN. As in Social Security Number.
24. Give the boot: OUST.
26. Boomer's kid, perhaps: XER. Generation X (1965 ~ 1980) is the demographic between the Boomers (1946 ~ 1964) and the Millennials (1981 ~ 1996).
27. Sty emanation: ODOR. // And 45-Across. Sty emanations: OINKS.
29. Maker of Regenerist products: OLAY.
31. Bath tourist spot: SPA.
34. First __ equals: AMONG. Also the name of a 1984 political novel by Jeffrey Archer (b. Apr. 15, 1940).
36. Pogo stick sound: BOING.
37. Toy that resembles a gyroscope: TOP.
38. Rafael who is one of tennis's "Big Three": NADAL. The Big Three in tennis refers to Novak Đoković (b. May 22, 1987), Roger Federer (b. Aug. 8, 1981) and Rafael Nadal (né Rafael Nadal Parera; b. June 3, 1986), each of whom is considered to be among the greatest players. [Name # 2.]
39. Healthcare.gov law, for short: ACA. As in the Affordable Care Act.
40. Chi-town airport: O'HARE. Ever wonder why the airport code for Chicago's O'Hare International Airport is ORD? It was originally named Orchard Field Airport for the neighborhood in which it was located. It was renamed in 1949, in honor of aviator Edward "Butch" O'Hare (Mar. 13, 1914 ~ Nov. 26, 1943) who went missing in World War II. [Name # 3.]
42. Nothing to do with soccer?: NIL.
43. Boo-boo: ERROR.
46. World Cup cheer: OLÉ. A crossword staple.
47. Wonderland bird: DODO. Think of Alice. I understand that just yesterday Alice met a Cheshire Cat.
48. Abbr. on a company sign: ESTD. As in Established.
49. Promissory note: IOU.
50. "My only __ sprung from my only hate!": Juliet: LOVE. A reference to a play by Willie the Shakes. [Name adjacent.]
52. "To a degree": -ISH.
55. Church deliveries: SERMONS.
59. Artist with the 2024 album "Cowboy Carter": BEYONCÉ. Beyoncé Giselle Knowles (b. Sept. 4, 1981) is married to Jay-Z (b. Dec. 4, 1969), whose given name is Shawn Corey Carter, but is that why she had Carter in the name of the album? [Name # 4.]
61. Slowpoke's opposite: SPEED DEMON.
63. Petri dish gelatin: AGAR.
64. Ebbing and flowing: TIDAL.
65. Old movie spool: REEL.
66. Answering system limbo: HOLD.
67. Clotted cream accompaniment: SCONE. Yummers!
68. Site for selling personalized gifts: ETSY.
69. Multitool's multiplicity: USES.
Down:
1. Cuts with a sickle: REAPS. Sometime it can be pretty grim.
2. Singers between sopranos and tenors: ALTOS.
4. Itsy: TINY.
5. Route around a construction area, say: DETOUR. There is some major road construction on the interstate in my city for the next [fill in the blank/taking bets] years.
6. Denim pants: JEANS.
7. Rocky Mountain National Park grazer: ELK.
8. One who adds a little color: DYER.
10. Aquatic mammal: OTTER.
11. Better __ ever: THAN.
12. Try out: TEST.
13. Boats like Noah's: ARKS.
19. Austinite, e.g.: TEXAN.
28. Personal code?: DNA. Cute clue.
30. Story teller?: LIAR.
32. Chorizo meat: PORK.
33. "Planet of the __": APES.
34. __ Domini: ANNO. Today's Latin lesson.
35. Pigeonhole filler: MAIL.
36. Storyteller: BARD. THE Bard is Willie the Shakes.
41. Double or triple, maybe: HIT. Think baseball.
44. 18 holes of golf, typically: ROUND.
48. In equal amounts: EVENLY.
49. "To be clear ... ": I MEAN.
51. Double-reed woodwinds: OBOES. A crossword staple.
53. Ascend, as a peak: SCALE.
54. Giraffe groups: HERDS.
55. Phased-out jets: SSTs. These jets used to be a crossword staple.
56. __ fail: EPIC.
57. Upgrade, as decor: REDO.
58. Parched: SERE.
60. Banzai Pipeline island: OAHU. I am not a surfer, so was not familiar with the term Banzai Pipeline. Apparently it is a famous surfing spot.
62. Rendezvoused: MET.