Flibber-Flabber is a dietary food that is meant to help someone lose weight, but a ton of it has to be eaten to make any noticeable progress. Flibber-Flabber is produced from the mouth of the Flibbius Flabbius plant and is commonly known for being "straight nasty" (as described by Mung). The only character in the show who seems to like Flibber-Flabber is Chowder.
Flibber-Flabber appeared in "The Flibber Flabber Diet" when Truffles put everyone on a diet to see who could lose the most weight the quickest. Despite the fact it is supposed to help the consumer lose weight, Chowder had gained a great amount of weight after consuming tons of Flibber-Flabber; the opposite of its intended purpose. Truffles was able to lose at least a single pound from consuming a decent amount of it, though. This implies that Flibber-Flabber does indeed work, however, poor portion control could lead to gaining weight instead of losing it.
Flibber-Flabber takes the appearance of a translucent, gelatinous, green substance. It is possible to successfully integrate Flibber-Flabber into various dishes, though attempting to do so in order to make the its taste more tolerable will prove fruitless.
As demanded by Truffles, Mung Daal had attempted to put Flibber-Flabber into various dishes in order to make it easier to consume it. The dishes he made with the Flibber-Flabber included: processed Flibber-Flabber, a sandwich, pizza, a cake, and pancakes. None of these dishes were able to make the substance taste any less nasty.