Vowel Progression: A E I O U and Sometimes Y.
18-Across. MI5 headquarters named for a London river: THAMES HOUSE. Built in 1930, the building has housed M15 only since 1994.
23-Across. TV show intro tune: THEME SONG.
42-Across. Boss Tweed's caricaturist: THOMAS NAST. Although he was born in Germany, Thomas Nast (Sept. 27, 1940 ~ Dec. 7, 1902) is considered the Father of the American Cartoon. He created many political cartoons, especially of Boss Tweed during the 1870s. He is also credited with creating the GOP Elephant and the modern version of Santa Claus.
Across:
1. Cuba, por ejemplo: ISLA. Today's Spanish lesson. Cuba is an Island.
10. Hard-to-describe sensation: VIBE. It could be an eerie sensation.
14. Évian evening: SOIR. Today's French lesson. Évian is a brand of mineral water Évian from sources near Évian-les-Bains, in eastern France.
15. Levels of society: STRATA.
16. A party to: IN ON.
20. From Canada's capital: OTTAWAN. Hi, CanadianEh!
22. Genre that represents things as they are: REALISM.
26. Asian kebab: SATAY. Satay is a Southeast Asian dish of skewered, seasoned grilled meat. I have also heard of a vegetarian version of the dish.
27. "Who wants my jellyfish? / I'm not sellyfish!" poet: NASH. Ogden Nash (né Frederic Ogden Nash; Aug. 19, 1902 ~ May 19, 1971), was an American poet, best known for his humorous poetry. He even rated his own US postage stamp.
28. Seeker of "the way": TAOIST.
37. Play a part (in): ACT.
38. Boardroom VIP: CEO. As in the Chief Executive Officer.
40. The Beatles' "__ Mine": I, ME.
41. Santa __ winds: ANA. [Note: There should be no tilde over the N in the word Ana.]
46. Splash sound: PLOP.
48. Meticulous to a fault: ANAL.
50. Humana rival: AETNA. Both are health insurance companies.
64. Maggie Simpson's sister: LISA. What would a crossword puzzle be without a reference to The Simpsons!
65. Avatar of Vishnu: RAMA.
66. Chef's array: SAUCES.
67. Browse (through): LEAF.
68. What "lama" has, as opposed to "llama": ONE L. Another snippet from Ogden Nash. The poem goes as follows:
The one L Lama, he's a priest
The two L Llama, he's a beast
And so I'll bet my silk pyjama
There isn't any three L Llama
Legend has it that a fire chief replied that his department occasionally responded to a three L Lllama.
70. Type of prof.: ASST. As in an Assistant Professor. A new Ph.D. must work her way through the ranks of Assistant, then Associate, before becoming a full professor at a university.
Down:
1. Childish comeback: IS NOT!
2. Truth, to Shakespeare: SOOTH.
3. Hears out: LISTENS TO.
5. Prefix with centric: ETHNO-. As in Ethnocentric.
6. Historic time span: ERA.
8. Old Roman road: ITER. In present day, ITER (International Thermonuclear Experimental Reactor) is the international fusion research and engineering magaproject.
9. Let up: EASE.
10. Break, as laws: VIOLATE.
11. Aleut relative: INUIT.
12. __ nova: Brazilian dance: BOSSA. João Gilberto (June 10, 1931 ~ July 6, 2019), a Brazilian musician, was known as the "Father of the Bossa Nova." The bossa nova is a style of Brazilian music that became popular in the 1950s and 1960s.
21. Director Craven: WES. Wes Craven (né Wesley Earl Craven; Aug. 2, 1939 ~ Aug. 30, 2015), is best known for his horror films, such as Scream and Nightmare on Elm Street.
24. Utmost degree: Nth.
29. Fail to include: OMIT.
31. Bowler or derby: HAT. Did you know that the Bowler and the Derby are the same hat? The Derby Hat is the term used in the US, while across the pond, the term is Bowler Hat.
32. Otto's "Oh!": ACH. Today's German lesson.
33. Theater award named after Antoinette Perry: TONY. I didn't know this, however, having the first name in the clue, it was easy enough to get to Tony. Antoinette Perry (née Mary Antoinette Perry; June 27, 1888 ~ June 28, 1946 ) was an American actress and stage director. She was the co-founder of the American Theatre Wing, which is an organization to support the theater. It is this organization the now presents the Tony Awards.
34. Misconceptions: FALLACIES.
38. Savory finger food: CANAPÉ. Yummers!
39. Wits' end?: ESS. The last letter of the word "Wits" is an "S".
43. Least possible: MINIMAL.
45. It might be elementary: Abbr.: SCH. As in an Elementary School.
48. Stockpile: AMASS.
49. "Will & Grace" network: NBC.
50. The Jetsons' dog: ASTRO.
51. Wharton's "__ Frome": ETHAN. This book is on my To-Be-Read list, but is so far down on the list that I probably never will read it.
52. "I'm almost afraid to tell you" response: TRY ME!
54. Encouraged: URGED.
58. In __: existing: ESSE.
59. Inbox annoyance: SPAM.
Here's the Grid:
I'll leave you with a QOD: If you can convince yourself that you look fabulous, you can save yourself the trouble of primping. ~ Andy Warhol (né Andrew Warhola; Aug. 6, 1928 ~ Feb. 22, 1987)