Answer: Vicious vs. Viscous
Inquiring minds want to know the difference between vicious and viscous.
Although these adjectives look similar both beginning with vi, ending with us, and having a jumble of vowels in the middle mixed in with the letter c they actually have no relationship at all beyond the fact that both come from Latin roots.
Viscous, Webster's tells us, comes from the Latin for "full of birdlime." Although we're more likely to curse as we wipe sticky tree sap from our windshields, rather than think of it as a useful adjunct to hunting small birds for dinner, the stuff had much the same reputation in Roman times as it does now: gummy and hard to wipe away. Viscous, by extension, means thick and gluey:
"Kanda-kun, you've added too much tapioca to the raspberry puree the filling's completely viscous now," chided Ono.
Kanda gaped at the sticky mass clotting the big mixer. "Master, it's horrible! What do I do now?"
Vicious, on the other hand, is from the same Latin root as vice. It has a number of negative meanings, the most familiar of which is currently "dangerously aggressive" or "marked by violence or ferocity":
"Keep down that racket in the kitchen, will you?" Tachibana groaned as he leaned against the display counter. "I've got a vicious hangover!"
Try to remember that although being attacked by a vicious animal or tormented by a vicious rumor can both lead to sticky situations, the word viscous is not what you should use to describe either problem! It might help to exaggerate the differences in pronunciation in your mind's ear: "VI-shus," (which sounds like ferocious, malicious, and other fearsome adjectives) versus "VISS-kus" (with its hard k, like thick and sticky).
Postscript: smillaraaq pointed out that I was thinking of the wrong bird-related sticky substance in my derivation for viscous. I have edited one sentence to take care of the problem. Thanks, imouto-chan!