Made some research and found a "dat fart though" comment in the discussion for this anime special:
Saiki Kusuo No Ψ-Nan Kanketsu-Hen

Obviously that says nothing. Might be referring to an "old fart", to a fake fart (in the context of the show, as in some character believes another character farted even though they didn't), an ugly woman's fart or a guy's fart... but it could also mean a pretty woman's fart. If nobody saw it, we might have to go check it out.

It's on youtube (albeit with Indo sub) but right now I don't have 46 minutes to watch it, so if anyone is up for the challenge and the bet...
youtube.com/watch?v=Zn7tqqC9a2o

If not, eventually I'll watch it myself (it seems like a funny anime anyways so it won't be boring, especially if I manage to find eng sub).