Theme: Olive Garden - because they have the Never Ending Pasta Bowl. The endings of the themes are types of pasta, as the unifier in the SE reveals.
18A. *Sculling competition craft : RACING SHELL
28A. *"Support our troops" symbol : YELLOW RIBBON
47A. *Convenient neckwear : CLIP-ON BOWTIE
62A. *Disorder on the court : TENNIS ELBOW
55D. Food found in the shapes at the ends of the answers to starred clues : PASTA
A hungry Argyle here. I'll cut my comments short so I can get to breakfast. Eggs and spaghetti.
Across:
1. Co. with brown trucks : UPS. A Splynter shout out, first thing.
4. Eat with relish : SAVOR. Savor the flavor.
9. Brand-new barker : PUPPY. Aah!
14. Vietnamese holiday : TET
15. Yale or Root : ELIHU. Elihu Root was Secretary of State, 1905 – 1909.
16. Be in harmony : AGREE
17. Fiancé's last words? : "I DO"
20. "Toreador Song" opera : "CARMEN". 22. Cheers for Escamillo in 20-Across : OLÉs The glamorous toreador.
23. Zing : PEP
24. Annual fact book : ALMANAC
26. __ of office : OATH
33. Singer Guthrie : ARLO
36. Historic women's gp. : DAR. (Daughters of the American Revolution)
37. Comic actor Dudley : MOORE
38. Middling mark : CEE
39. New Jersey port with a bridge to Staten Island : BAYONNE
42. Slipshod : LAX
43. "Speak of the __!" : DEVIL
45. Prefix with -lithic : NEO. Neolithic, the last phase of the Stone Age.
46. Liquefy : MELT
51. Without repetition : ONCE
52. Develop stage fright, say : TENSE UP
56. "Me time" resort : SPA
59. Lady of Lisbon : DONA
61. Freeport's "Grand" island : BAHAMA
65. "Pygmalion" playwright's initials : GBS. George Bernard Shaw (1856–1950)
66. Els with tees : ERNIE. Bert is his caddie.
67. Big name in metal wrap : ALCOA
68. Permit : LET
69. Buddies, in slang : PEEPS. Your people, your posse.
70. British comedian Gervais : RICKY
71. History chapter : ERA
Down:
1. Seat of New York's Oneida County : UTICA. An area well known to some of our solvers.
2. Sewing machine lever : PEDAL
3. Thunder source : STORM
4. Cool and collected : SERENE
5. Hawkeye Pierce portrayer : ALAN ALDA. M*A*S*H
6. London's Old __ : VIC. (theatre)
7. Buckeye State : OHIO
8. Get close to "Empty" : RUN LOW
9. Fritter away the hours : PASS TIME
10. "Blech!" : "UGH!"
11. GRE practice : PREP. (Graduate Record Examinations)
12. One-named soccer immortal : PELE
13. Website with restaurant reviews : YELP. And more. LINK
19. Transmission choice : GEAR. This had me looking for a type of transmission, not just one gear.
21. BLT dressing : MAYO
25. Medium for some animators : CLAY. Claymation they call it.
27. "Game of Thrones" network : HBO
29. Maine campus town : ORONO
30. Tree trunk : BOLE
31. Like Sabin's polio vaccine : ORAL
32. Bank teller's cry : "NEXT!"
33. Outlet letters : AC/DC. Not both on the same outlet, I hope.
34. Lively dance : REEL
35. First name in jeans : LEVI
39. Brownies with brown sugar in place of chocolate : BLONDIES. Guess what? It's safe to google 'blondies image'.
40. Pond critter : NEWT. Needed perps to decide which critter it would be.
41. Small laptop : NOTEBOOK
44. Much-hyped NASDAQ event for Facebook : IPO. (initial public offering)
46. Fry basket material : MESH
48. Cpls. and sgts. : NCO's
49. Remain close to : BE NEAR
50. Sort of : IN A WAY
53. Soaring hunter : EAGLE
54. "Raw" pigment : UMBER. As opposed to 'burnt'?
56. Staircase part : STEP
57. Famille patriarch : PÈRE. in France.
58. Writing sister of Emily and Charlotte : ANNE
60. "That's __ need!" : ALL I
63. __ in the bud : NIP
64. Send covertly, as a dupe email : BCC. The original recipient won't see a copy has been sent.
Argyle
