There is disagreement among readers as to whether they were built by Agatha or were found by her in the hangar, although the former seems more likely.
Although they at first appear to be a cross between a mechanism and living swine, as more of their internal structure is revealed on subsequent pages, they seem to be pure clank.
Their name is a bit of a puzzle as well. (A reader noticed that it could be a pun on "pork choppers.") The Professors Foglio had Agatha refer to them as "Schweincopters." They could also be referred to as Fliegendes Schwein, which is German for Flying Pig.