Here's the link to download all 3 of them: DOWNLOAD
Here's a link to information and download links for Paintown: LINK
After downloading the file, unzip it and transfer the folders over to:
via ftp or a file manager such as multiMAN. Then they should appear in Paintown and be playable the next time you run it.
Shadow The Hedgehog
Zero (from Megaman)
Download: Opium2k's Characters (all 3)
Paintown: Info & Download