The Celtic Snail is a green-tinted snail that appeared on billboards and in advertisements, all over Ireland in late 2000. Has now sadly joined the list of creatures great and small killed off by (and created by) the wrath of advertising, since the campaign has since ended.
It was all Fine Gael's idea. They believe that the "Celtic Tiger" is/was slow and snail-like. Personally, I would suggest that if they're trying to win electoral support, they might just want to get themselves some policies. But then what would I know?