I put alot of time into this, its basically a super good version of
SmashGpsp. Here it is:

Overview:
Terdinglage has put together what he calls the SmashPack. It is a
version of SmashGpsp which contains 12 bonus levels he created and 12
of the best custom characters out there. Easily installed by
extracting the .zip to the root directory of your PSP, its a great way
to enhance your SmashGpsp experience. Terdinglage felt the pack could
be put to better use, so he approached PSPBrew.com with turning his
pack into one of Brew's unique Pack Generators. Monkeymaximus, the
site's admin accepted his request, and here's what he had to say.

"Within the next few days, we will be releasing a new version of our
one of a kind Pack Generator - the SmashPack Generator. We'd like to
give special thanks to Terdinglage for developing the levels and
constructing the pack as without him this wouldn't have been possible.
The SmashPack Generator will give you the ability to choose from a
list of all the currently available levels and characters that you
want in your version of SmashGpsp. This allows you to have your own
unique version of the game, with the characters and levels YOU want,
not what the developers want! To top it all off, it will be just as
simple as our original Pack Generator. Just run the auto-extracting
zip and install to the root of your PSP."

Here are the current lists of characters and levels the Generator will have:

Character List:
Chrono, Chun Li, Contra, Coolspot, dante, Forte, Goemon, Gold Elite,
Guile, Harpuia, Inuyasha, Jack, Link, Luigi (original), Majin Yusuke,
Mario (original), Master Chief, Mecha Sonic, Megaman, Megaman Zero,
Metool, Moriya, Pacman, Qwest, Retro Link, Riku, Rockman, Samurai
Jack, Samus, Shadow, Sonic, Sora, Tails, Trunks, Wolverine, Zero.

Level List:
Bowser's Dungeon, Dark Citadel, Deathstar, Mario World, Shark's Mouth,
Pokemon Stadium (original), High (original), Blue Sky (original), Pipe
Dream, Mario and Luigi Flyby, Mario World Basic (originally Small xx),
Mario Brothers 3, Hell on Earth, Sunray, Mario World, Shinobi.

Want to download or discuss the SmashPack? --> http://www.pspbrew.com/forum/viewtopic.php?p=4768#4768

Are we missing a character or level? Please post here --> http://www.pspbrew.com/forum/viewtopic.php?p=4767#4767