This guerilla campaign from 2006 is from BUND, the German Friends of the Earth. They want consistent ecological politics.
At this campaign members of the BUND put globe-ballons on exhaust-pipes of cars in Berlin, Germany. The emissions inflate the ballons. And after the message (The world can't take anymore CO2.) is readable, there is a big bang.
Of course the text is not always readable anymore after the big bang but the campaign gives a lot of rumour and media attention.

Agency: Butter.Berlin (Germany)
Creative Director: Timm Holm, Michael Preuss
Art director: Björn von Buchholtz
Copywriter: Hermann Weiss
Photographer: Paul Seitz
Thanks Bjorn for sending