This is a fun section with official downloads I've kept throughout the years featuring Gengar. You'll find wallpapers and other stuff that were available on official Pokemon sites.

PC Downloads

Escape from Gengar's Mansion!

Obtained On: The English Pokemon site after beating the Escape from Gengar's Mansion! game. Gengar lives in a mansion and tries to trick you so you can't escape!

PC Downloads

Are You Really Scared? Pokemon

Obtained On: The special Ghost themed Japanese Pokemon site after beating the Gengar game. (ぬけだせ！ゴーストポケモンの館 )The site features a collaboration with famous horror manga artist, Junji Ito. It took me a long time to beat because it's all in Japanese and it was a time limit game! The site is still working but in case it's taken down, it can be viewed on the Wayback Machine here.

Japanese Name: 本当は怖い? ポケモン

I probably butchered the translation for the English name.