Theme: Bumps in the night - or daylight. Some words that can be placed ahead of BUMP.
18A. Vodka brand with flying birds on the bottle: GREY GOOSE. Goosebump.
23A. Racing bike: TEN SPEED. Speed bump. Only ten speeds on a racing bike, how quaint.
35A. One "there on the sand," in a 1974 hit by The First Class: BEACH BABY*. Baby bump, an expression for showing a pregnancy.
49A. Symbol of absolute rule: IRON FIST. Fist bump, handshake for germaphobes?
55A. Disagree ... or, literally, what the last words of 18-, 23-, 35-, and 49-Across can be: BUMP HEADS. The last words can head up a BUMP phrase.
Argyle here with a debut from Mr. Sharp He debuted in NYT in 2002 and has numerous puzzles in compilation books. He has done some punny work in the past but this is a straight forward "word goes with word" puzzle. Sorry, nothing to do with Independence Day.
1. Crowd noises: ROARS. "Oohs and aahs" could have been fitting crowd noises for tonight's fireworks.
6. "Is that __?": "No kidding?": A FACT
11. Fat meas.: BMI. (Body Mass Index)
14. __ sanctum: INNER
15. Jar Jar Binks' planet: NABOO. from Star Wars.
16. Olive product: OIL
17. __ Park: San Diego Padres' home: PETCO. Pet supplies retailer Petco is based in San Diego.
20. "__-haw!": YEE
21. Link with: TIE TO
22. Dol. parts: CTs. $ & ¢
25. Muse of comedy: THALIA. The eighth-born of the nine Muses.
28. Dodge City's state: KANSAS
29. "Pop goes" critters: WEASELS
30. Man-mouse connector: OR A
31. "Melrose __": PLACE. Seven seasons on Fox.
34. Jason of "How I Met Your Mother": SEGEL. His role was Marshall Eriksen.
37. Groucho's smoke: CIGAR
40. Waste maker, per a proverb: HASTE. "Haste makes waste"
41. Santa __, Calif.: ANA
44. Art exhibition site: GALLERY
46. Learn about: HEAR OF
48. Tristan's beloved: ISOLDE. Extensive Wiki article.
51. Dallas home of the NCAA's Mustangs: SMU. (Southern Methodist University)
52. Second rock from the sun: VENUS
54. Barrister's practice: LAW
57. "Water Lilies" painter Claude: MONET
59. Mrs., to Claude: MME. French abbreviation for Madame.
60. Jazz great Shaw: ARTIE
61. Hawaiian veranda: LANAI
62. Take the plunge, in a way: WED
63. Small plateaus: MESAs
64. Sports data: STATs
1. "Let 'er __!": "Fire away!": RIP
2. Subscription period: ONE YEAR
3. Cell reception aid: ANTENNA
4. Schoolyard playtime: RECESS
5. "No more seats" Broadway sign: SRO. (standing-room only)
6. Actress Dickinson: ANGIE. Remember her?
7. Managed: FARED
8. Aid in crime: ABET
9. Road Runner's pursuer: COYOTE
10. Dress fancily, with "up": TOG
11. Illegal, like movies on file-sharing sites: BOOTLEG. Odd clue.
12. Rocket, for one: MISSILE
13. Suffix with percent or project: ILE
19. Irish playwright Sean: O'CASEY. 1880 – 1964 (seems obscure)
21. Maker of the first electric sports car: TESLA
23. Fight ender, briefly: TKO.(technical knockout)
24. Covered decoratively, as walls: PAPERED
26. One whose star has faded: HAS BEEN
27. Comm. for the hearing-impaired: ASL. (American Sign Language) Comm. can be an abbreviation of communication.
29. Complex patterns: WEBs
32. "__ Breaky Heart": ACHY. Popular song by Billy Ray Cyrus.
33. Half a dance: CHA
35. Shape, as dough: BALL UP
36. A Musketeer: ATHOS. "D'Artagnan, Athos, Aramis and Porthos"
37. Movie SFX: CGI. (special effects/computer-generated imagery)
38. "It seems to me ... ": "I ASSUME ... "
39. Latched (onto): GLOMMED
41. Journalist Huffington: ARIANNA. She was the co-founder and editor-in-chief of The Huffington Post, which is now owned by AOL.
42. "Piece of cake": "NO SWEAT"
43. Rearward, on board: AFT
45. Midnight rider Paul: REVERE
47. On the water: AFLOAT
49. Nepal neighbor: INDIA
50. Ploys: RUSES
53. Has a bite: EATS
55. 7 Series automaker: BMW
56. Hawaiian-style pizza topping: HAM
57. L.A. Galaxy's org.: MLS. (Major League Soccer)
58. Apt "it's" anagram: 'TIS