A Different Journey: Anticlimax, the name suggests...

Anticlimax: a drop, often sudden and unexpected, from a dignified or important idea or situation to one that is trivial or humorous. 
Also a sudden descent from something sublime to something ridiculous. In fiction and drama, this refers to action that is disappointing in contrast to the previous moment of intense interest. In rhetoric, the effect is frequently intentional and comic.

Where the Term comes from !!!

The term Anticlimax comes from the combination of two Greek words: anti, which means "against" or "the reverse of," and klimax, which means "a ladder" and was derived from klinein meaning "to slope."

Examples

1. Novels

Oh, poor Mr. Jones," mourned Mrs. Smith, "Did you hear what happened to him? He tripped at the top of the stairs, fell down the whole flight, banged his head, and died.". " Died?" said Mrs. Robinson, shocked. "Died!" repeated Mrs. Smith with emphasis. "Broke his glasses, too."

(Isaac Asimov, Isaac Asimov's Treasury of Humor. Houghton Mifflin, 1971)

Examples from Pride and Prejudice by Jane Austen.

Pride and Prejudice!

1.     The ladies were somewhat more fortunate, for they had the advantage of ascertaining from an upper window, that he wore a blue coat, and rode a black horse.

2.     He begged pardon for having displeased her. In a softened tone she declared herself not at all offended; but he continued to apologize for about a quarter of an hour.

3.     Mr Collins had only to change from Jane to Elizabeth – and it was soon done – done while Mrs Bennet was stirring the fire.

4.     …his friend Mr Darcy soon drew the attention of the room by his fine, tall person, handsome features, noble mien, and the report which was in general circulation within five minutes after his entrance, of his having ten thousand a-year.

2. Songs
And as I'm sinkin
The last thing that I think
Is, did I pay my rent...

(Jim O'Rourke, Ghost ship in a storm)

3. Movies

A famous example is the ending of The War of the Worlds, where, amidst the chaos of the extraterrestrial takeover of planet Earth, the aliens are defeated by the most unexpected organism: the common cold. Another example could involve the protagonist faced with insurmountable odds and ultimately being killed, without accomplishing their goal, despite what appears to be a turning point for the character.

4. Quotes

"The holy passion of friendship is of so sweet and steady and loyal and enduring a nature that it will last through a whole lifetime, if not asked to lend money." — Mark Twain