Overview
Poniko (ポニ子, "Ponytail girl") is a character appearing in Madotsuki's dream. She is popular with fans. Her house is found by diving into a pool located in an igloo at the Snow World.
Description
Poniko is a blonde girl with a ponytail, green shirt, a brown skirt and red shoes and with (possibly) blue eyes. She, like Madotsuki herself, lives alone in a very bare house. She seems to want to be alone, as Madotsuki is only able to reach her house by going through The Pink Sea. At her house there is not much to interact with except a light switch. There is a 1/64 chance that Poniko will change into Uboa after flicking on and off the lights.
It is also known by fans of the Nintendo game Mother/Earthbound, that outside of her house looks a lot like the location Magicant in Mother 1/ Earthbound Zero. Mainly because many areas in Yume Nikki are inspired by Mother 1.
The blue things on her face can be eyes or tears.
Fan Speculation
Character
Some say Poniko is a seperate entity all together while others say she's Madotsuki's ideal person, her "hero" to look up to, a nice normal girl with flowing hair,in the manga Madotsuki even says "I wonder if she'll be my friend" and "Her Clothes are cute too" and when replaced by Uboa when Madotsuki gives up after flipping that light switch so many times. It's also been speculated that she saved Madotsuki's life (possibly from a car wreck) but the memory of her death haunted Madotsuki, taking form in Uboa.
It is still unknown which one of them (Poniko or Uboa) is the good one. Uboa might be evil because it can teleport Madotsuki to the inescapable room with water (or blood) on the ground. Poniko might be good, but no one can be for sure. It is also thought that Poniko may also be a bit arrogant or just wants to ignore Madotsuki as she doesn´t react when Madotsuki tries to interact with her. Poniko may dislike Madotsuki or has bad memories about her. Her transforming into Uboa could be an angry reaction to Madotsuki when she gets on her nerves for fllicking on and off the lights, or because she just angered her.
Room
Poniko and her room could be interpreted as early designs of a protagonist and her room, due to familiar aspects seen in Madotsuki's room.
Actions
No matter what you do, she doesn't seem to pay any attention to you, which is the point of some fandom hilarity. The only exception to this is running at her with a knife and using the cat effect. This is a trait shared by many characters, however.