I must have a thing for Citroens, as this is the third one I've 'ratt-ified' so far...
No, it's not a bathtub, or an egg. It's a '24 5CV powered by an air cooled three cylinder made from a halved Corvair six. No idea if the seats on it vibrate, like on a modern Citroen, but maybe they do.
As always, the link to the bonus footage:
http://public.fotki.com/ChuckMost/rat-alley/24-citroen-c-bucket/