The Melancholy of Hattoushin Mona (８頭身モナーの憂鬱, Hattōshin Monā no Yūutsu)¹⁾ is a brief AA Flash animation and screamer that borrows Hattoushin Mona and >>1-san. It does not have a credited author, though it spans as far back as November 2003.²⁾

We are introduced to Hattoushin sighing about >>1-san, set to a calming piano tune,³⁾ when >>1-san shows up right in front of him. In response, Hattoushin starts breathing heavily, uttering “haah, haah… today's the day…!” (ﾊｧﾊｧ…、今日こそは…！), then the scene is suddenly interrupted by a scream along with a picture of what appears to be a jagged-teeth zombie with Escher's eyes⁴⁾ somehow edited onto him.

Hattoushin: *sigh*… >>1-san…
>>1-san enters.
>>1-san: Haah, haah…
Hattoushin: Haah, haah… today's the day…!
Screamer.

• The animation is roughly 23 seconds long and, given the format, would start automatically.
• It probably isn't older than September 2001⁵⁾ or newer than November 2003.⁶⁾
  • At the time, Haruhi Suzumiya was still a light novel, but it is entirely possible that the animation's name is a parody of the first novel, The Melancholy of Haruhi Suzumiya.
• The jumpscare image might possibly stem from the “Isolated Horror Room” (戦慄の隔離部屋, Senritsu no Kakuri Heya), which was a horror-themed GeoCities Japan website.
• If you're morbidly curious about what the aforementioned jumpscare looks like, you can easily find it by looking up the Japanese filename in Google or looking at the Flash file's thumbnail.

• The Melancholy of Hattoushin Mona on the Must Not Search Wiki [JA]
• The Melancholy of Hattoushin Mona on Screamer Wiki [EN]