Thats glorious, gotta remember that one.

Chan is a japanese name ending for children, various communities have created several Anime mascots over the years. Theyre generally suffixed with that -tan, as a cute misspronounciation of chan.

https://en.m.wikipedia.org/wiki/OS-tan

Btw, 4tan should be that 4chan mascot. Ive seen it previously on sankaku complex, but its been too many years ago. Cant find it right now.

/Edit: i probably should mention that you shouldnt visit sankaku complex at work. Its very... Questionable with nudity