"Dance of the Hours". it just reeks of atmosphere. One would have to listen to David Ogden Stiers' narration in the "Making of Fantasia" documentary on the original DVD release to get the full effect.
Although it doubles as terrifying, Chernabog raising his arms to the final stings of Night on Bald Mountain.
Followed by him being driven back by the heavenly bells. His power is staggering, but he has such a simple Weaksauce Weakness...
What drives it home is the progression of Chernabog's expressions each time the church bell rings. First it's confusion, then annoyance, then an amazing Oh, Crap!... and finally, the sound of the church bells have him in physical pain.
The "Night on Bald Mountain"/"Ave Maria" combo. After terrifying audiences with one of the scariest characters Disney's ever devised, the coming dawn brings with it the best possible reassurance that there are still things to hope for. Gorgeous.
Here's something about the making of that segment. The whole "Ave Maria" segment had to be refilmed twice (once due to having the wrong lens on the camera, and a second time after an earthquake disrupted the session) and the final filmreel was flown from Hollywood to the New York premiere just four hours before showtime.
When it was released in 1940, Fantasia was the most expensive film Disney had made, and it was a complete critical and financial flop. Its failure nearly bankrupted Disney, and was one of the biggest reasons (other than World War II) that the studio didn't put out any full-length animated features in the eight years between Bambi and Cinderella. Nowadays, it is often regarded as not only Disney's best feature, but as one of the greatest films of all time, making Fantasia a standout example of Vindicated by History.
Most of the time, Toccata and Fugue in D minor is performed on an organ, but Fantasia opens with a full symphonic arrangement of the song that is sure to enrapture the audience immediately. What better way to begin Fantasia than this sheer Awesome Music? There is also something about the vague, surreal imagery that accompanies Toccata and Fugue (in comparison to, say, the more story-driven imagery of Rite of Spring) that somehow serves to highlight the beauty and intensity of the music greater than any other imagery could have done. The kicker is the very end of the piece which seamlessly synchronizes erupting water jets with Stokowski's conducting motions, and the final image of Stokowski silhouetted on a sunset as the final, haunting passage of Toccata and Fugue plays is guaranteed to hold viewers in awe at the combined evocative power of music and imagery.
The image of Mickey Mouse shaking hands with Leopold Stokowski, symbolizing the meeting of the old and new art forms.
Several Mama Bear moments during the "Pastoral Symphony" section:
When the storm first begins to hit, several unicorn foals hide under their mother for protection. She stands defiant to keep her babies safe.
The pink Pegasus foal is being blown to and fro in the storm, failing to right herself. In one swoop, the mother Pegasus comes and helps her baby get safe. When the Pegasuses are in shadow, it can be seen that even the mother Pegasus has trouble flying in the storm, but she does it to save her babies, and when the lightning flashes again, all of the foals can be seen safely under their mother's wing.
While not an actual mother bear, a unicorn foal is helplessly bleating for aid on a rock as the storm rages. A centaurette wades into the water and safely rescues the foal. Later, when the centaurs are seen running into a cave for shelter, the foal can be seen carried to safety in the centaurette's arms.