How did that huge fountain fit through the door?

Not to mention all the pipes and such to keep the water flowing, fountains like that don't just work without plumbing lol.

"Mr. Treehorn treats objects like women, man."

Haha it's on now and I was just thinkin that but then was like, eh it's a movie.

Here's what Ron Howard had to say in the DVD audio commentary about why audience members were WILLING to suspend their disbelief over the water fountain appearing in Allen's room, despite the fact that the door was too narrow for the fountain to go through:

"My theory about this kind of thing is that you earn the right to stretch the truth and stretch the logic by being logical. So if you set up a world and you establish a kind of a credibility and the characters are winning, and the audience is going with the story, that at a certain point if you want to take a leap, they'll go with you. I don't think you could do this in the first ten minutes of the movie."

Not only that, but about when he said "Awww, you sold your necklace." What were the stones that would have fetched so much money?

In movies like this, they also like to throw in something almost as absurd as the whole storyline- so audiences will pick apart a little thing like this rather than the whole idea of a mermaid and man hooking up 20 years after a chance encounter when they were kids... or the existence of mermaids, period.