1. __ Cong
2. Works at a museum
3. Won at musical chairs
4. Without a care in the world
5. Watering aid
6. Vatican City is one
7. Usually
8. U.S.-Canada defense system
9. Twisted shape
10. TV channels 2 to 13
11. Tuxedo part
12. Tuna at a sushi bar
13. Toothpaste-endorsing gp
14. Sweetie, in dialect
15. Surprise victory
16. Summit-ending agreement
17. Summer treat
18. Sty mother
19. Stuck (to)
20. Start of a sequence ending in 'thx'
21. Solitary
22. Skatepark feature
23. She, in São Paulo
24. Rare bills
25. Quite a long while
26. Prefix meaning 'ten'
27. Pointy hat wearer
28. Place for a ring
29. One called Miss
30. Olympics segment
31. Old Voice of America overseer: Abbr
32. Okinawa okay
33. Of assistance
34. Odds partner
35. Nile snake
36. Log-on needs ... and, literally, what the ends of 16-, 23-, 37- and 56-Across can be
37. Like the bikini in a 1960 #1 hit
38. Like some tuxedo shirts
39. Like Dumbledore and Santa Claus
40. Lends a hand
41. It's said that he said, 'I never said most of the things I said'
42. It used to be plenty
43. Iron alloy
44. Hi-__ image
45. Hand-held cleaner, briefly
46. Gung-ho, as a fan
47. Gridiron squads
48. Funny Cheri
49. Frozen convenience store offering
50. Fr. holy woman
51. Flew the coop
52. Fictional visitors from space
53. Feed the kitty
54. Extension on an unformatted document file
55. Eponymous electrical current principle
56. Dislike intensely
57. Dipped chip
58. Delicate handling
59. Deceptive measure
60. Cuatro y cuatro
61. Courtroom VIPs
62. Clove crusher
63. CIA relative
64. Campus mil. group
65. Call for pizza, say
66. Burton of 'Roots'
67. Buckwheat noodle of Japan
68. Big band venue
69. Arrive at
70. Actress Mila
71. 25% of M
72. 1970 John Wayne film
73. '__ what I mean?'
74. 'That was a close one!'
75. 'Stillmatic' rapper
76. 'Slithy' thing in 'Jabberwocky'
77. 'I think,' in chats
78. 'Absolutely!'