(more situational comedy pranks than a one liner or joke per se)
(when offering someone a cup of tea, premake them, and make them with gelatine, to turn them into a solid block. Then eventually, after claiming there is nothing wrong at all, and they must be drinking it wrong, give them the real hot cup of non-solidified tea)
The counterpart to this, needs keeping in the fridge. The gallium spoon. A teaspoon cast from an impression taken in clay etc or other suitable mold, cast in gallium, or gallium-a low percentage of indium. You do warn someone before they try to swallow any, although the alloy or metals aren't toxic, but it has a REALLY low melting point. Depending where you live you might try it or not be able to, because it'll melt in the hand if kept there. So quickly, after making your gallium-indium alloy spoon, you put it on a teacup saucer, and to keep it away from the heat, carry the tea.
The mark is to be offered sugar, and proffered the tea, and the spoon on the saucer. Mark picks up spoon, stirs tea, and then the spoon doesn't come back out of the tea, just a nub of handle thats likely to melt away from between their fingers. Followed by a mock bollocking for just destroying the priceless family silver heirlooms or something similar. Or 'don't you KNOW how low the melting point of platinum is?? (it really, really isn't low melting point metal, Pt is fucking hard to melt. You can't do it with a charcoal fire, although the ancient mesoamerican culture group had some societies that could work platinum with pyrometallurgical techniques, mixing Pt dust panned from a river with alluvial gold dust, and a little silver, which unlike the very high melting and corrosion resistant platinum can be worked with a charcoal-based flame and bellows etc. to cast it, and as an alloy, can be sintered together from the alluvial platinum dust, as IIRC it was the aztec, or possibly maya, possibly both, who mastered the technique long before we europeans even discovered the element Pt, and they'd melt them together as an alloy, then melt out the gold, allowing for malleable platinum to be worked, and sintered together from dust that we couldn't work, and indeed was so tough that it'd shut down silver mines if it was present.
Quite clever, I think, for such supposed primitives. Got to admit, I love ancient technological studies
Stuff like ancient chinese multiple rocket launchers, repeating crossbows, even an automatic magazine-firing flywheel-powered catapult, and of other civilizations, flamethowers and a hideous anticavalry weapon using a piston-powered siphon mechanism to fire the toxic, blinding, flesh-corrosive sap of the tropical Euphorbia plants (Spurge family, nasty lot but some much worse than others), and at close range, they'd fire the these poison-guns into the faces of the cavalry horses, making them go berserk due to getting a face full of the phorbol ester nasty ass shit (one example, resiniferatoxin, is a capsaicin-like entity in what it does, only its a hyperpotent TRPV1 superagonist, packing about 16 BILLION scoville-units of virulent burning corrosive 'heat'. About a thousand times as potent as pure capsaicin from chili pepper.)
Not that I'd actually approve of using such a thing in this day and age, but that sort of thing had to be some weapon up close to break a cavalry charge and turn an enemy's horses into as big a threat to their own men as they would have been to yours, especially if the resources for a phalanx, or similar technology was not in use. These poison-gunners would have been effective, and a reconstruction done the weapon itself IIRC had a range of about 15 to a bit over that in feet.