Puzzle

 ACROSS

  1 Voice above tenor

  5 ___ Forces Day

 10 Treaties may end them

 14 Jug plug

 15 Polynesian people

 16 Frequently

 17 Possible result of microwaving fast food without unpacking it?

 19 Revere took a famous one

 20 Naughty child

 21 Prefix for "verse"

 22 "For ___ waves of grain"

 23 Cookware breakout session in culinary school?

 28 Word before "branch" or "bread"

 30 Little pitchers have big ones

 31 Dog biscuit shape, often

 32 Join forces

 33 Robust energy

 36 Deeply impress?

 39 Go back over

 41 Agreeable response

 42 Absorbent cloth

 44 Mars, to the Greeks

 45 Frilly fabric

 46 Pennsylvania sect

 47 Song about summer in the Golden State?

 53 Products of the mind

 54 Question of identity

 55 Frat member

 58 Christmas carol ... or, read as two parts, a theme hint

 59 Retriever serving as a guard dog?

 63 Instrument with a head

 64 Extraterrestrial

 65 Vehicle at a weigh station

 66 Org. that ships boxes

 67 Reproductive plant body

 68 Egyptian cobras

DOWN

  1 Opening at the opera?

  2 Appear as a threat

  3 Outward signs

  4 Green-lights

  5 Modify, as the Constitution

  6 Forearm bones

  7 Unruly crowd

  8 Stretch with a name

  9 Play in a sandbox

 10 Reheats

 11 Excuse of the accused

 12 Cowboy contest

 13 Ship's rear end

 18 Something to hum

 22 Good memory, e.g., for a crossword solver

 24 State as true

 25 "O say can you ___ ...?"

 26 Keep in stock

 27 Impulse

 28 Do as directed

 29 ___ wolf (independent person)

 32 Thanks, in Tours

 33 X and Y, commonly

 34 Chills, as crab legs

 35 Fabric with holes

 37 Uplifting mythological figure?

 38 Calf meat

 40 Malek of "Bohemian Rhapsody"

 43 NBA official

 46 Shortly, poetically

 47 Like the goddess Lakshmi

 48 Litter box emanations

 49 Start a round of golf

 50 Says "There, there" to, say

 51 One with a title

 52 German wine valley

 56 Way off the highway

 57 Japanese sashes

 59 Used to be

 60 Mont Blanc, e.g.

 61 Summer Olympics site after London

 62 Fed. property manager

Solution