My worst day was when we were at the Magic Kingdom on the Saturday of the U.S.'s Columbus Day Weekend holiday. It's a three day weekend that most people get off from work and school around the country, but for some reason the state I lived in at the time never celebrated it.
So we were totally caught off guard when the Magic Kingdom almost reached *capacity*, on a supposedly "low season" October day.
It might have been manageable even given that, but both the Haunted Mansion and Pirates of the Caribbean went down for several hours from some computer problem, and my parents were traveling with us and insisted on going on coasters and stuff I couldn't bring my one year old on, so I was often left just sitting with my baby son waiting on other people, in shoulder to shoulder crowds. We would have hopped, but my cheapskate parents only bought a one park per day ticket, wouldn't spring for hoppers.
We tried to eat dinner at Columbia Harbor House and for some insane reason, they had closed the upstairs, and the downstairs was wall to wall people and trash and spilled ketchup and drinks on the floor.
At the end of the night, after the fireworks, the lines trying to get out of the park and onto the monorail or ferry to the TTC were an hour long in and of themselves.
The park staff were completely overwhelmed, and all in all that day just absolutely sucked.
That was the beginning of my Disney trip planning obsession! The next time we went to Disney together, they bought the tickets I told them to, and followed my well laid out trip plan, and we all had a much happier time. And I NEVER go to WDW on Columbus Day weekend, which is a shame, because it's my son's birthday, usually, but it's just not worth it.