Interestingly the Thing was on ITV last night and I ended up watching bits of it!
I think what's great is that you never know who the Thing is. The bit with Nauls/Childs and Garry on the sofa is great because you just know one of them is the Thing...and then none of them is! Similarly the fact that Norris has a heart attack surely means he can't be the Thing but he is! Copied him perfectly, even down to a heart defect.
Yeah I'm not sure what it says about my memory, but I watch this movie about once a year, and I always seem to have a hard time remembering exactly when or where certain characters have been taken over. lol