Hoo-boy...this theme took me some time to figure out. Since I wasn't getting too many answers, I was pretty sure we were looking at a rebus (or cram-a-lot) of some sort.
Double letters within one square...and it all came together quite nicely.
17A: "Scram!" (buzz off), crossing at 3D: Half of a showy display? (razzle) and 14D: Like some oil rigs (offshore).
18A: Practice area, of a sort (putting green)...one of the best of the bunch...crossing at 7D: Kennel club rejects (mutts), 9D: Overwhelm (boggle) and 11D: Lee Van __ (spaghetti western actor) (Cleef).
28A: "Black rat" as opposed to "Rattus rattus" (common name), crossing at 21D: Eponym of a classic Minnesota-brewed beer (Hamm) and 26D: __ time (in no). Hamm was my tip-off.
36A: Biblical patriarch whose name means "he will laugh" (Isaac), crossing at 31D: TV's Jack and kin (Paars).
41A: Radical Hoffman (Abbie), crossing at 33D: Robot in "Forbidden Planet" (Robby). Abbie would have been another tip-off, except I spelled it Abbe for too long.
46A: Northeast, on a map (u pp e rr ight), crossing with 38D: Spice holder (pepper box) and 43D: Misses the mark (errs). I had top right until I figured out the theme...and I never would have guessed pepper box. Thank goodness for its cross at 67A: Lawless role (Xena).
59A: Directories (address books), crossing at 55D: Less conventional (odder), 46D: Amherst campus, briefly (U Mass) and 56D: Blackmore heroine (Doone).
62A: Bygone women's magazine (McCalls), crossing at 58D: Stops on a sales rep's rte. (accts) and 52D: Last place (cellar). This corner really had me fouled up. Because I had appts, rather than accts, I couldn't come up with the name of a magazine to save my soul.
At that point, I declared the puzzle finished and checked out that nasty little corner at JimH's blog.
I think Alan Arbesfeld's idea was brilliant, and he pulled it off pretty well. It may be asking too much to expect that no double letters would appear in separate squares...1A: Factory seconds: Abbr. (irrs), 23A: __ Snider, frontman for rock's Twisted Sister (Dee) 63A: Sharp (keen) and 53D: Seconds: Abbr. (assts).
Other noteworthy fill includes 24A: Once-in-a-lifetime traveler (Haji), 54A: Silk fabric for scarves (foulard), 12D: Cigarette brand that sponsored "The Dick Van Dyke Show" (Kent), 25D: Bump (jostle) and 28D: Grammy winner Winans (CeCe)...although I wasn't sure if it would be CeCe or BeBe.
Don mentioned that 66A: Himmel und __ (traditional German potato dish) (erde) actually translates to heaven and earth. I'm sure there's a story behind that.
I definitely don't get 37D: Job for Hercule Poirot (CAS)...what am I missing?
I missed a golden opportunity yesterday...the perfect segue at 30A: Concluding appearance (swan song). I don't know how long it will be, but for the time being, Madness is signing off. I've neglected some pretty important things to keep this blog going. I will miss it, and I will miss many of you. [UPDATE for those of you in Syndication Land. The sabbatical was short-lived...I missed all of you too much. Check out the links in the sidebar for the next week or so...but come back to Madness soon!]
Here's the grid...
...and I'll see you later.