The Department of Improbabilities deals with elements in fic that are highly unlikely but not yet at the level of WTF (there's another department for that). It used to be the Department of Ah, Hell Naw!, but apparently there were objections to that name and it was changed accordingly. Fittingly, this department is headed by the Reannual, one of the most improbable plants in the multiverse.
Mission reports from this department are listed on The Complete List of PPC Fiction, Department of Improbabilities.
"Interlude 03 - The Reannual", Agents Mittens and the Radioactive Moss Creature