One way to understand and appreciate Claude Coats' contribution to the HM might be to review what exactly it was that he did in his 54-year career at Disney and to see how those special skills are showcased in the finished attraction. This is not by any means a full survey of Coats' work, of course; there are other places to find that.
A Career in Quick Review
No question about it, Coats belongs on the short list of all-time greatest Disney Imagineers. He joined Disney about the time that work on Snow White was beginning to accelerate. Coats was a background painter, eventually becoming a color stylist as well. He was happy to stay in that area, which seems appropriate, since he was a quiet, polite, self-effacing guy, showing little inclination to call attention to himself. They called him the "gentle giant" (he was a little over 6' 6"), and people who worked with him recall a gifted, amiable, and exceedingly generous colleague and mentor.
As background artist and color stylist, he worked on every Disney animated feature from Snow White to Lady in the Tramp, plus innumerable shorts. Dude. Already with Pinocchio and Fantasia, his concept sketches and backgrounds were widely admired around the studio.
The precise extent of Coats's contributions to the other two 1955 originals, Snow White and Peter Pan, is less clear, but there seems to be little doubt that he participated. Later dark rides in which he was heavily involved include Alice in Wonderland and Adventure Thru Inner Space (which was practically all Coats; notice that there are no characters in ATIS).
It had a swell soundtrack too. I've added the sound of waterfalls and fountains, for a more virtual experience. As I recall, the water sounds were at least as loud as the music.
Rainbow Caverns with Water Sounds
Coats was paired with Marc Davis in the development of Pirates of the Caribbean. In general, Coats created the sets and Davis created the characters (although that's a bit of a simplification). Coats was very much the architect in charge, very hands-on.
So, is that it? Coats was the architect of the house; Davis created the characters unliving in it. Somehow that analysis seems insufficient. There is such a different set of vibes coming from the two Imagineers that something more seems to be involved. It's not just spooky vs. kooky either.
The Painting as Gateway
Marc Davis produced umpteen haunted portrait concepts, not only changing portraits, such as you see in the final product, but talking portraits, portraits in which one character moves to another, and other varieties. For a time, it seems they were thinking of including that hoariest of haunted house clichés, the portrait with shifting eyes.
If you think about it, any artist like Davis or Coats who paints in a representational style is already engaged in illusioneering. You feel as if you are looking through a window into a real, dimensional world; or if it's a portrait, you feel as if you are in the presence of an actual person. It's so fundamental that we normally don't even think about it, but it is true nonetheless that paintings can be downright eerie, without them even trying for that particular effect. It's no wonder that enchanted paintings are a stock item in the annals of the supernatural. You already find one in The Castle of Otranto, the first Gothic novel, written by Horace Walpole in 1764. In it, a figure steps right out of the frame of a painting.
The gag has often been recycled since. W. S. Gilbert (of Gilbert and Sullivan fame) used it in Ages Ago, an 1869 stage musical, and again in Ruddigore (1887). Notice how this 1870 London Times illustration of the scene in Ages Ago (right) even mimics an old illustration of the similar scene in Otranto (left).
Being the character animator par excellence, Marc Davis's natural inclination was to see a haunted painting as a portal through which a character comes from there to here, interacting with us on this side. That's the tradition, going back at least to Otranto. There would seem to be little interest in the world on the other side of the painting once the character has left it. Look what's left of that pirate portrait once the pirate has stepped out of it.
Some of Coats' published Haunted Mansion artwork is quick-study stuff. There's a mood, but you don't necessarily feel . . . , you know, sucked in.
After examining the Fantasyland dark rides, with their blend of 2D and shallow 3D, bathed in the magic of black light, is there any doubt how this scene would have been accomplished? So cool. And this:
Who would not love to see how this would have been done? The whole drawing depicts a dissolve between there and here, inside and outside, human artifice and wild nature. This is not an exit point for characters stepping over into our presence; this is a place that invites you to enter.
When Marc Davis tried to depict this same sort of erasure of the boundary between inside and outside, he was far less successful. Too much focused on the characters, I imagine.
the inky blackness . . . sorry, Marc, but you should leave this sort of thing to Claude Coats.
The chandelier may have been the source for projecting little blobs of light that turn into faces...
Note how the teapot gag in the graveyard was originally intended as a ballroom gag, with wine. Makes more sense. The teapot ghost is the only ghost at the graveyard jamboree who is still completely invisible!
Again, the draftsmanship. Look how well the tricky shadows of the dancing ghosts are rendered. And here's the detail in this familiar sketch most easily overlooked: dozens of orange footprints, left by the dancers all over the floor.
Every time you feel that strange urge to wander into the labyrinthian depths of the Haunted Mansion and be lost (the pull is especially strong in the first half), that's Claude Coats the background painter, leaving your very self to supply the missing character cel.