- Acclaimed Flop: Reviews and players immediately fell in love with the game, but it was way too unique and strange to be a big seller. The fact that it got almost no promotion didn't help either.
- The game's infamously hideous North American cover art is considered to be a major reason it flopped in the US.
- Christmas Rushed: The reason why the NTSC version is stripped down compared to the PAL and Japanese versions of the game. This was corrected in the re-release.
- Hey, It's That Voice!: Misa Watanabe as the Queen! You wouldn't recognize her from Vivi's voice… better from EVA's. The fact she has to speak in two different Conlangs doesn't help…
- What Could Have Been: ICO was originally intended to be a PS1 game. Footage of the prototype can be seen here.
- While on the outside of the Castle, particularly at the start of the path to the Western Reflector, some of the tiles are almost blindingly white. This must be the original appearance of all the exterior tiles, at least on the front of the Castle in the Mists.
- This may have been taken from the Pyramids of Egypt. Originally they were completed covered in a shimmering white stone. To quote Wikipedia, Most pyramids had a polished, highly reflective white limestone surface, in order to give them a shining appearance when viewed from a distance. Imagine what the Castle must have looked like new.