There is a straight, narrow path that leads to the Toriningen Party from the Wilderness that plays a surprisingly upbeat tune in contrast to the usually dreamy background music in Yume Nikki. When Madotsuki enters the area where the party can be seen, the music gets louder.
There appears to be two towels with green cups, a yellow cake, and riceballs on them at the party. There are also three cubes with frowning faces on them (the same kind that are often seen in the Wilderness) and a boom box. The boom box seems to be what is playing the music.
Some fans interpret the Toriningen Party as a party that Madotsuki wasn't invited to, or a social status that a person can't reach, no matter how hard they try.
A Youtube video of the Toriningen Party . It also shows the Toriningen's reactions to the Stoplight and Cat effects.
A video of a player hacking to get in the party, removing the Toriningen and adding the four most known monochrome characters can be watched here.