RE: Super Mario 3 Time Attack

I know this isn’t a reply about the actual Super Mario 3 game, but in general it’s a reply about the fact that some people have too much time on their hands to make some things…anyways

So after watching the many Mario videos recently, I wanted to show this video of SMW, where the designers made a unique level and added a song in the background.  The cool thing is, everything the player/mario does in the game, corresponds with the beat and music that is playing, check it out.

I’m really curious on why and when Designers have this time to create something like this.

If you were a designer, would you have the time and patience to slowly plan everything out and create a level where it would fit exactly to the beat of a song?  Or would you rather spend that time on something more important to you?
 It just makes me question at how far people will go to just satisfy themselves in making something that takes alot of effort and time, and probably does not pay them in any way for what they did.