Crossword: ''That's a Tough One''

Across
1 "Welcome Back, Kotter" star Kaplan
5 Unpleasant atmosphere
11 He hosted a reality show called "I Pity the Fool"
14 Vows sometimes rushed in comedies
15 "The Other ___ Girl" (2008 Natalie Portman movie)
16 "Star-Spangled Banner" contraction
17 Five on a dude's foot?
19 Clay, later
20 Passover dinner
21 "Put Your Head On My Shoulder" singer Paul
22 "Kilroy Was Here" band
23 Co-star of Morgan and Baldwin
25 Chunky milkshake ingredient
27 Words before "fire" or "emergency"
32 BFFs
35 "Are we there yet?" answer, maybe
36 Time off from the group?
40 Former NHL star Robitaille
41 Thorny trees
42 Co. whose mascot is Nipper
43 The right amount to be serendipitous?
45 "Win, Lose or Draw" host Convy
46 Herb that's also a name
47 Old-school fastener at the roller disco
49 Hit for ZZ Top
52 Bread for a reuben
53 Madcap
56 Sitcom starring a singer
59 Big name in handbags
63 Vexation
64 Ad line that caused a Muppet to answer "You bet me do!"?
66 Turn down
67 More level
68 "So Big" author Ferber
69 Nyan ___ (internet meme)
70 Nissan model
71 Awestruck response