I presume you mean the scene on the last page but one, where one of the rebels is excited to see the boat with the General and his associate who have been taken prisoner by Spirou and Fantasio (and was the basis for the book cover).
It's a nod from the translators. Not a very good one, if you ask me, since the rebel is supposed to be obsessed with explosives, not the weather.
In the original French, he shouts "mille pétard" ("thousand bangers" or "thousand firecrackers"). Maybe he should have said something like "I'll be blowed!", as in "blown up". |