Puzzle

 ACROSS

  1 Word repeated before "sis boom bah"

  4 Only a female one can sting

  8 Latin clarification

 13 "Of course!"

 15 "Quickly!"

 16 Any Best Picture winner

 17 Amount with no wiggle room (see letters 1 to 3, 6 to 9)

 19 One of the Pointer Sisters

 20 Cold comfort?

 21 Deer skull extension

 22 Athos, to Aramis

 23 Cold side at a deli

 24 Palindromic drink

 27 Milk-producing animals from France's mountains (3 to 6, 8 to 10)

 33 Made tracks

 35 Pre-stereo

 36 Weasleys' owl

 37 Edible submarine

 38 Colorful card game

 39 Irritate

 40 Protective suit

 42 Takes home

 44 Big name in locks

 45 Appliance combination that can be stacked (2 to 4, 8 to 10)

 48 Retired flier: Abbr.

 49 Vow renewal vows

 50 AFL's partner

 52 Weekly medical journal, with "The"

 55 "___: Endgame" (2019 Marvel Studios film)

 60 No longer groggy

 61 Tree texture, or a hint to each starred answer's pair of hidden words

 62 Internet connection device

 63 Start the pot

 64 Conclusion starter?

 65 Enjoys toys

 66 Kernel, e.g.

 67 Test site

DOWN

  1 Widespread

  2 Largest continent

  3 German word that doesn't rhyme with "sir"

  4 "Saving Private Ryan" or "Dunkirk"

  5 Skeptical response

  6 Anatomical pouches

  7 N95 masks and such, briefly

  8 "Everything gets done"

  9 "It's all right!"

 10 Live the wrong way?

 11 Web search result

 12 Cloth concern

 14 Jane Austen heroine Woodhouse

 18 Mountain lion

 21 Drink that may be amber

 23 Stuck-up

 24 "Phooey!"

 25 Drama with 30-Down

 26 Wavy 'dos

 28 Flour bag measures

 29 Word before "circle" or "peace"

 30 Long solo songs

 31 Bridge payments

 32 Messy weather

 34 Whatchamacallit

 41 Cashes in

 43 Officially withdrew

 46 Root problem

 47 The letter "O" resembles one

 51 Folklore monster

 52 Floor or table fixture

 53 G.I. no-show

 54 Zilch

 55 Top-notch

 56 November 2020 choice

 57 Rank above viscount

 58 Capital of Latvia

 59 Highbrow person

 61 "Now where ___ I?"

Solution