You missed the funniest bits. There is a very long dirt bike scene and police chase. The Milland/Grier monster steals a dirt bike along with black doctor Don Marshall, seeing an obvious stunt man with a dummy Ray Milland head zooming around on the bike was hilarious. When they meet up with Grier's girl friend (played by Laugh In regular Chelsea Brown), she asks "Do you have two of anything else?" There is a dinner scene where bigoted Milland doesn't like the soul food being served, he asks "What's for dessert? Watermelon?"
The "Oh Happy Day" scene at the end had me dying!" The song was a bit hit for the Edwin Hawkins Singers in 1970, 2 years before this movie and it was sung by some other singers here.
Sven did a very funny song parody about the "Rosey/Ray" monster as he called them, done to the tune of the "Rosie O'Grady" song.
He was also pretty thorough with the trivia on the cast, though I wish he could have included more on Ray Milland. He does mention his Oscar winning The Lost Weekend and Frogs another ridiculous film he made the same year as Thing With Two Heads., it seems he was taking any role during this time. I wish Sven mentioned the classic ghost story with Milland The Uninvited (1944) as well as X-The Man With The Xray Eyes (1963) which I love.