Put down dial drumstick and start decking the halls. As their promotional and commercial spheres expand, the big holidays are now tripping over each other’s heels more than ever. This is a transition week, when TV is chockablock with both Thanksgiving and Christmas specials. On T day (Nov. 26), NBC broadcasts the annual Macy’s Parade (9 A.M. ET), with Willard Scott and Katie Couric as hosts, while Comedy Central again offers a 30-hour marathon (from 6 P.M. the previous night until midnight on Thanksgiving) of the delicious spoof series Mystery Science Theater 3000. That means a nonstop barrage of such bad movies as Teenagers from Outer Space, with the attendant scathing comments of our stranded spaceman, Joel, and his witty robots, Tom Servo and Crow. (It’s better for the digestion than the traditional Thanksgiving viewing option: NFL football.) The very next night (Fri., Nov. 27), CBS airs It’s Christmas Time Again, Charlie Brown (8:30 RM. ET). A lot has changed in the 27 years since the last Peanuts Yuletide special, but not in the cloistered cartoon world of Charlie and Linus, who in this sweet hall hour take in a school pageant together. Saturday (Nov. 28) brings Neil Diamond’s Christmas Special on HBO (10 P.M. ET), an incredibly pompous, carol-filled extravaganza. Hearing Diamond’s zircon-quality versions of “While Christmas” and “Jingle Bell Rock” will have you pining for Mitch Miller. Also beginning this weekend, and running through December (check local listings), independent stations around the country will be showing the 61st annual Hollywood Christmas Parade. The grand marshals are that inseparable, often insufferable couple, Tom and Roseanne Arnold. So Happy Thanksgiving. But as you tuck into that meal, remember: 28 more shopping days.