I had no idea this film existed until last night. It's currently available on the Criterion Channel. Trippy and often psychedelic, my first thought was to never *ever* watch this while I have a fever. And an aside: the Spelling Bee is adorable.
The animation seems a little rough and a little rushed, but what the hell, it's Chuck Jones. Lots of familiar voice actors and singers if you've ever watched any Chuck Jones animated anything. And - obviously - it's based on the famous children's book The Phantom Tollbooth. I think the main selling point for this film is the off-the-wall animations.