stuffed knup-knups are a trade commodity 1) or 'junk' that is used as a way of gaining revenue in the game EVNova; this revenue would then be used to buy important things like ship upgrades and weapons, and dumb things like drop-bear repellent.
Also present in several of the less important side-plots of the game.
2) Sometimes used as an inside joke/insult to suggest that someone tends to buy stupid, unneeded things.
1) ISNN reports that the price of price of stuffed knup-knups on Sirgil III is high.
2) Can I sell you some knup-knups?