Theme: Easter is April 16, in case you've taken a break from Mass since Christmas.
20. Postgraduate degree: MASTER OF ARTS
36. Mob kingpin: MAFIA BOSS
41. Vase material named for its white color: MILK GLASS
54. Turning point in tennis, and a hint to this puzzle's circled letters: SERVICE BREAK
Argyle here with C.C. back for another puzzle. Back to back can't happen very often. Do note MASS is split three ways: 3/1, 2/2, and 1/3.
1. Tie up at the pier: DOCK
5. Basics: ABC's
9. Expressive chat image: EMOJI. Emoticon on steroids.
14. "That works for me": "OKAY"
15. "Dang!": "DRAT!". (It didn't work for me!)
16. Cars sold at auctions: REPOS
17. Nabisco chocolate-creme cookie: OREO
18. Vermeer or van Gogh: OIL PAINTER
22. First-class: A-ONE
23. Sailor: TAR
24. Tanning lotion letters: SPF. (Sun Protection Factor)
27. Golf hole benchmark: PAR
29. Snacked (on) to excess, briefly: OD'ed. (overdosed)
32. Pinup queen Page: BETTIE. Don't tell Mrs. Claus.
34. __ buco: veal dish: OSSO
38. PG-13 issuing org.: MPAA. (Motion Picture Association of America)
39. __ vincit amor: OMNIA. (love conquers all)
40. Restful resorts: SPAs
43. Window insert: PANE
44. Wiped off the board: ERASED
45. Genghis __: KHAN
48. '60s tripping drug: LSD. (Lysergic acid diethylamide)
49. Took command of: LED
50. "Morning Edition" airer: NPR. (National Public Radio)
52. Lion's den: LAIR
59. Casino big spender: HIGH ROLLER. Lets me out.
62. Veggie in a green smoothie: KALE
63. Sleep lab study: APNEA
64. Where Norway's Royal Family resides: OSLO
65. Biblical paradise: EDEN
66. L.A.'s region: SOCAL. Southern California
67. Pics on ankles: TATS. (tattoos)
68. Hair-coloring agents: DYES
1. Gloom partner: DOOM
2. Cajun veggie: OKRA
3. Course including romaine and croutons: CAESAR SALAD
4. Greenhouse gas protocol city: KYOTO
5. Loved to death: ADORED
6. Get-up-and-go: BRIO. 1725-35; < Italian < Spanish brío energy, determination < Celtic *brīgos; compare Old Irish bríg (feminine) power, strength, force, Middle Welsh bri (masculine) honor, dignity, authority
7. New cow: CALF
8. Mar. 17th honoree: ST. PAT. Timely.
9. Horn of Africa nation: ERITREA
10. Clothing store department: [MENS]
11. Withdraw, with "out": OPT
12. G.I. doll: JOE
13. Dead Sea country: Abbr.: ISR. (Israel)
19. Lawrence's land: ARABIA
21. U2's "The Joshua Tree" co-producer Brian: ENO
24. "Enough!": "STOP ALREADY!"
25. Residents around the Leaning Tower: PISANS
26. __ up: came clean: 'FESSED
27. Saddle knob: POMMEL
28. Aim high: ASPIRE
30. Madame Bovary: EMMA. Debut novel of French writer Gustave Flaubert, published in 1856.
31. Language of Copenhagen, in Copenhagen: DANSK
33. Culinary meas.: TBSP. (tablespoon)
35. Acorn droppers: OAKS
37. Pike or trout: FISH
39. Seasoned expert: OLD PRO
42. Army leader: GENERAL. Usually, an old pro.
46. Last Olds models: ALEROs, but they live on in crosswords.
47. Catch red-handed: NAB
51. Place to keep a camper, for short: RV LOT
53. Irritated: IRKed
54. Mets' old stadium: SHEA
55. "Casablanca" woman: ILSA
56. Boston NBAer: CELT. Boston Celtics, timely also.
57. Protected from the wind: ALEE
58. Some male dolls: KENs
59. Owns: HAS
60. NASDAQ debut: IPO. (initial public offering)
61. Health supplements co.: GNC. Read about a Saint Patrick's Day Link.