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⁾

The animation uses an intentionally quiet 20-second excerpt of Beethoven's Sonata Pathétique, while it features Hattoushin sighing about >>1-san before he shows up. As the routine goes, his appearance excites Hattoushin, then the animation is abruptly interrupted by a scream and a heavily-modified 'horror' image, which seems to depict a jagged-teeth zombie with Escher's eyes³⁾ 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 can't be older than September 2001, or newer than November 2003.⁴⁾ It isn't known how popular the 'Melancholy' title was, or if the Haruhi Suzumiya light novel releasing in 2003 was a factor.
• The jumpscare image might've came from a horror-themed GeoCities Japan website, supposedly named the 'Isolated Horror Room' (戦慄の隔離部屋, Senritsu no Kakuri Heya).
• If you are morbidly curious about what the aforementioned jumpscare image 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]