Installation: extract the archive to /usr/kde/3.5/share/emoticons directory (or similar, system-wide, root privileges needed, preserve permissions recommended) or home directory (theoretically, i haven't tried it yet)

Tip: you can use this theme in Konversation too.. Open the ~/.kde/share/config/konversationrc config file and in section [Themes] add these lines:

EmotIconTheme=Critters
EnableEmotIcons=true

(But no idea, why they are so small there..)

The icons are from http://jisp.netflint.net