Grandson: Aw grandma, that sure was sweet of you, but ou know that I don't eat left overs.
Dad: Hey you little un-grateful Fuck Weasel. You take those leftovers and thank your grandmother.
A fuckweasel will always avoid telling a direct lie in case they are exposed, giving them plausible deniability or letting them fall back onto "a misunderstanding" excuse, such as;
Boss> "I spoke to Steven and he said he'd written that report you said you'd done"
Weasel> "Ah no, sorry you must have misunderstood, I just came over earlier to tell you it was completed."
The "boss" in this case has no comeback as the fuckweasel is technically correct, although it is clear what the inference was in the original conversation.
A good fuckweasel will pick his or her stories cleverly to lower the chance that a discovery will occur.