Sonic Adventure Gaiden

Sonic Adventure Gaiden was a parody game created by Kulock of The Moogle Cavern in 2001. Released at a time when most Internet users had 56K connections, the 15MB download proved to be disappointing for many.

Background
In 2001, fan games were becoming increasingly "flashy", routinely showing off custom sprites and backgrounds, MP3 soundtracks, and unique game engines (often with special gameplay mechanics, and always with a multitude of classic Sonic features). Stories tended to pick up on the then-new Sonic Adventure.

Kulock sought to parody this with his first fan game: Sonic Adventure Gaiden. Set immediately after the events of Sonic Adventure, the game had music and backgrounds ripped directly from the Dreamcast original, heavily edited SA-like sprites, Sonic's new Homing Attack, even an English/Japanese soundtrack option.

Gameplay
Players were treated to an introductory segment in which Eggman, having escaped at the end of Sonic Adventure, returned to his Final Egg base in the Mystic Ruins to put his backup plan (alluded to in SA) into motion. Then Sonic appeared, intending to stop Eggman. The player was given control, and could jump and attack Eggman. After taking a single hit (which he made no effort to avoid), Eggman's Eggmobile exploded, and he retreated, shouting "No way!  I can't believe this!" in true SA style.

Then the ending credits rolled. The 15MB game (taking about an hour to download on dialup) contained roughly two seconds of actual gameplay.

Does he explained it's a hoax?
Yes.

On a page referenced during the credits (along with a minor "take out your frustration by blowing up a Kulock sprite" minigame), Kulock explained. His intent had been intended partly as a joke, partly as a demonstration of just what could be done with the resources available to a fan game creator, and partly as a warning to the fan gaming community: just because a game looks good in stats, screenshots, and soundtracks does not make it a good game. Some people were amused, as Kulock had intended. Others were angry; some didn't get the joke, some simply didn't find it very funny.

The posters at the Moogle Cavern's message board were for the most part not in on the joke, and were in fact just as surprised as everyone else to see the game end so quickly. (On the other hand, their respect for and experience with their administrator probably left them better prepared for such silliness.)  However, many assumed otherwise at the time, and as a result there was a brief campaign by several SFGHQers to "educate the MC", which ultimately succeeded only in being annoying.

Download & Reference
http://info.sonicretro.org/Sonic_Adventure_Gaiden