FishDOS
FishDOS is an april fools joke made by Party Escort Bot = Beans in real life on April 1st, 2015 and used on later days.
What is it?
FishDOS is actually, as its name implies, a drawing of a fish version of GLaDOS. It has 4 colored circles, each one representing a Personality Core. On it can be seen: a purple circle, a yellow circle, a blue circle, a red circle and what appears to be the Aperture Science logo with a closed orange portal inside.
About potential deletion of this page
Even though the name of the page looks like FishDOS, the page actually is User:Party Escort Bot = Beans/FishDOS, which means this isn't a wiki page but a page from MY user, just like Arrran Weeviling, you'll see he has a lot of page. The page looking like it's called FishDOS is made with a simple trick using DISPLAYTITLE.